How does HowBridge add the 6-digit postal code to a delivery address?
Which Chunghwa Post service does HowBridge use to add the 6-digit postal code?
It uses the Chunghwa Post 3+3 Postal Code Lookup Web Service. Following the connection application form, HowBridge registered 1 fixed IP address and sent the form, stamped with the company seals, to Chunghwa Post for review. The connection was confirmed working and went live on the production site on 2026-10-06. It is used in only one situation: your Taiwan delivery address has already passed house-number matching (for example, the Ministry of the Interior TGOS found the house number), but the Chunghwa Post National Standard Delivery Address platform (NSDA) did not return a 6-digit postal code. In that case the HowBridge server sends the matched house-number address (without name or phone number), 3+3 returns a 6-digit postal code, and it is stored with the recipient record. In the 2026-10-06 tests each call took about 0.06–0.13 seconds. 3+3 returns only a postal code and cannot tell whether a house number exists. Chunghwa Post approving the connection application does not mean Chunghwa Post certifies or endorses HowBridge.
This is a back-end step in which HowBridge completes the 6-digit postal code for a Taiwan home delivery address. You do not need to do anything extra. It is not address verification itself: whether a house number exists is decided by Chunghwa Post NSDA and Ministry of the Interior TGOS house-number matching, and 3+3 only adds the postal code after the house number has already matched. It is not a government certification: what Chunghwa Post approved was HowBridge’s connection application, and Chunghwa Post also states that 3+3 lookup results are “for reference when writing mail addresses and for use by Chunghwa Post mail-processing units to sort mail only.” Writing a 6-digit postal code also does not guarantee that a parcel will arrive or arrive sooner; delivery remains the responsibility of the courier that actually carries it. HowBridge offers China to Taiwan consolidation shipping only, its warehouses are only the Shenzhen consolidation warehouse and the Taoyuan Dayuan operations warehouse, and it does not offer purchasing agent services.
How did HowBridge obtain the Chunghwa Post 3+3 Postal Code Web Service?
The 3+3 Postal Code Lookup Web Service must be applied for on paper. Chunghwa Post’s connection application form states that the connecting IP is “1 group, fixed”; applicants that are not individuals must stamp the organization seal and the responsible person’s seal, and send the form in duplicate to the Mail Business Promotion Management Section of the Postal Service Department for review, after which the Information Technology Department completes system setup and testing. HowBridge’s application and go-live went as follows:
| Item | Details |
|---|---|
| Service applied for | Chunghwa Post 3+3 Postal Code Lookup Web Service (SOAP, System Interface Specification V1.0.3) |
| How we applied | Following the connection application form, we entered the fixed IP of HowBridge’s Taiwan server, stamped the form with HowBridge’s company seals, and sent it to Chunghwa Post for review |
| Connection check | On 2026-10-06 we called the service from the HowBridge server and received a normal response (HTTP 200) |
| Go-live | Live on the HowBridge production site on 2026-10-06 at 15:06. This service has no API key and recognizes only the fixed IP registered in the application; the website, App, and LINE never connect to Chunghwa Post directly |
| Function used | GetZipAddress: takes an address and returns a normalized address and the 6-digit postal code |
| Related services | HowBridge also started using the Chunghwa Post NSDA WebAPI on 2026-09-23, and has used Ministry of the Interior TGOS national house-number location matching since 2026-09-21 |
What Chunghwa Post approved was HowBridge’s Web Service connection application; only after approval is the IP registered by HowBridge allowed to query. This is not a certification or endorsement of HowBridge by the government or Chunghwa Post, and it does not mean the two parties have a partnership. The application form also states that the applicant “shall not use the returned information in any way harmful to” Chunghwa Post and must bear any liability arising from that use.
What is a 3+3 postal code, and what does the Web Service return?
According to Chunghwa Post’s description on the government open data platform, Taiwan has used the “3+3 postal code” since 2020-03-03, in order to “speed up mail sorting and help recipients receive their mail.” The official “Delivery segment range usage notes” explain how the 6 digits are made up:
| Part | Official explanation | Example |
|---|---|---|
| First 3 digits | In principle assigned by administrative district; on some road sections the first 3 digits differ from the district to make delivery more efficient | Wugong Road and nearby sections in Xinzhuang District, New Taipei City are delivered by the Wugu post office, so the first 3 digits are 248 |
| Last 3 digits 001–199 | Delivery range for ordinary residences | Ordinary house-number addresses |
| Last 3 digits 201–799 | Bulk codes for bulk delivery segments, such as government agencies, schools, companies, and buildings (apartment complexes) | National Taiwan University 106319 |
What is a delivery segment?
3+3 is coded by “delivery segment”, not one code per household. The official lookup page explains that “those labeled ‘odd’ are odd house numbers (lanes), those labeled ‘even’ are even house numbers (lanes)”, and “house numbers described as ‘and above’ or ‘and below’ include the stated number itself.” In other words, a run of house numbers on the same road shares one 6-digit code.
What does the Web Service return?
System Interface Specification V1.0.3 lists 3 functions: GetZipCode, GetZipAddress, and GetCityArea. The GetZipAddress function that HowBridge uses returns a JSON string containing the normalized address (Address) and the 6-digit postal code (ZipCode). The application form states “only 1 record can be queried per call.” The specification has no field that says whether a house number exists.
One extra field in the tests
In the 2026-10-06 tests the response also contained a field that the specification does not describe, AddressNotServed. Ordinary addresses returned N, while 觀高山1號 near Yushan in Xinyi Township, Nantou County returned Y. Article 49 of the Mail Processing Rules says that in places such as deep mountains and remote islands mail “may be delivered without following the address”, so this field may relate to non-address delivery. However, Chunghwa Post’s specification, application form, and public documents do not explain it, and HowBridge does not currently use this field.
When is 3+3 used for a delivery address, and how does it divide the work with NSDA and TGOS?
When HowBridge verifies a delivery address, it asks three official sources in order. 3+3 comes last and is responsible only for adding the postal code:
| Order | Source queried | What it does |
|---|---|---|
| 1 | Chunghwa Post NSDA (National Standard Delivery Address platform) | If Chunghwa Post has the address on record, the screen shows “郵政標準地址” (“Postal standard address”) and normally a 6-digit postal code comes with it, so 3+3 is not asked (in the few cases where the address is on record but no 6-digit code was returned, the NSDA standard address is sent to 3+3) |
| 2 | Ministry of the Interior TGOS house-number matching | When NSDA does not have the address or cannot be reached, this confirms the house number exists and shows “已比對到門牌地址” (“House-number address matched”), but TGOS does not return a postal code |
| 3 | Chunghwa Post 3+3 Web Service | Called only when the house number has already matched and the 6-digit code is still missing: it sends the matched house-number address (mostly the address matched by TGOS) and adds the 6-digit postal code |
| — | When nothing is found | 3+3 is not called. The screen shows “查無此門牌，請確認縣市、區域與門牌號碼是否正確” (no such house number; please check the city, district, and house number), and you can still save after ticking “我確認地址正確” (“I confirm the address is correct”) |
Why is 3+3 asked only after the house number matches?
Because 3+3 also returns a postal code for house numbers that do not exist (see the tests below: the non-existent 金山南路二段9999號 also returned a 6-digit code). If 3+3 were asked first, a mistyped address would be treated as valid. So HowBridge uses 3+3 to add the postal code only after NSDA or TGOS has confirmed the house number.
What happens if 3+3 cannot be reached?
Each 3+3 call waits at most 3 seconds, and the whole verification takes at most 8 seconds; when less than 3 seconds remain (that is, about 5 seconds or more have already passed), the step is skipped. The application form also says 3+3 has “irregular system maintenance, about 2 to 3 hours each time.” In these cases you simply do not get the 6-digit code; the house-number matching result is still shown as usual, and you can still save.
Where is the 6-digit code stored?
After you save, the system queries again in the background and records the verification status, the data source, and the 6-digit postal code in that recipient record. The Member Center screen does not currently show the 6-digit code; the “postal code” field on the form is the 3-digit code filled in automatically from the district you selected.
Test results: what does 3+3 return for which addresses?
On 2026-10-06 we called 3+3 GetZipAddress directly from the HowBridge server and recorded the Chunghwa Post NSDA result at the same time. All 12 public addresses returned HTTP 200 in 59–132 milliseconds each, and none contains any member data:
| Address entered | 3+3 returned | NSDA | Note |
|---|---|---|---|
| 臺北市大安區金山南路二段55號 | 106409 | On record, 106409 | Both agree |
| 台北市大安區金山南路二段55號 | 106409 | On record, 106409 | Both common written forms of the character for Taiwan work |
| 臺北市大安區金山南路二段５５號 | 106409 | On record, 106409 | Full-width digits also work |
| 臺北市大安區金山南路二段55號3樓 | 106409 | On record with the floor removed, 106409 | 3+3 also returns a 6-digit code when a floor is included |
| 臺北市大安區金山男路二段55號 | 106 (3 digits) | Not on record | A typo in the road name returns only 3 digits |
| 臺北市大安區金山南路二段9999號 | 106004 | Not on record | A non-existent house number also returns a 6-digit code, so 3+3 cannot be used to judge house numbers |
| 臺北市大安區查無此路999號 | 106 (3 digits) | Not on record | A non-existent road name returns only 3 digits |
| 桃園市大園區拔子林三路30巷8號 | 337013 | On record, 337013 | Both agree |
| 新竹縣北埔鄉拔子林三路30巷8號 | 314 (3 digits) | Not on record | Choosing the wrong county or city returns only 3 digits |
| 桃園市中壢區中山路100號 | 320676 | Not on record | Not on record in NSDA, but matched by TGOS: this is exactly the case where 3+3 adds the 6-digit code |
| 金門縣金城鎮中興路22巷11號 | 893016 | On record, 893016 | Outlying islands work too |
| 南投縣信義鄉東埔村觀高山1號 | 556006 (AddressNotServed is Y) | On record, 556006 | The only example that returned Y; its meaning is not explained officially |
1. For valid addresses the two sources agree: in the 7 tests where NSDA had the address on record (4 house numbers), the 6-digit code from 3+3 was the same every time. 2. 3+3 never says “not found”: typos and a wrongly chosen city return 3 digits, while a non-existent house number still returns 6 digits, so it can only add a postal code. 3. The key case it fills in: 桃園市中壢區中山路100號 is not on record in NSDA, and with 3+3 live, addresses like this one that pass house-number matching can now also store a 6-digit code (320676).
What do members need to do?
There is nothing to apply for or set up. Just enter your delivery address as usual:
1Choose the city, district, and enter the road and house number
In Member Center recipients, add or edit a home delivery address, and enter the floor as usual.
2Check the verification result
A green “郵政標準地址” (“Postal standard address”) or “已比對到門牌地址” (“House-number address matched”) means the house number matches; when candidate addresses appear you can press “套用” (“Use”).
3Save
After you save, the system completes the 6-digit postal code in the background; you do not enter it. You can also set up recipients through the HowBridge LINE Official Account or the HowBridge App, with the same verification.
Is my address sent to Chunghwa Post, and how long is it kept?
A delivery address counts as “contact information” under Article 2 of the Personal Data Protection Act, and is therefore personal data. HowBridge uses it only for shipping:
| Item | What we do |
|---|---|
| What is sent to 3+3 | Only the text of the matched house-number address (including village and neighborhood, without the floor); it contains no recipient name, phone number, or identity data |
| When it is sent | Only when house-number matching succeeded but the 6-digit code is still missing; an address for which Chunghwa Post NSDA already returned a 6-digit code is not sent to 3+3 again |
| Caching of results | Not cached: every lookup is made live, and the 6-digit code is stored only in the recipient record you save |
| System logs | Error logs record only the data source and the error reason, not member addresses |
| Privacy policy | The Privacy Policy already discloses that address verification uses the Chunghwa Post “3+3 postal code” service |
What are the limits of 3+3 postal code completion?
It makes recipient data more complete, but a few things are worth knowing:
It cannot tell whether a house number exists
3+3 is coded by delivery segment, and in the tests a non-existent house number also returned a 6-digit code. House numbers are judged by NSDA and TGOS; 3+3 does not affect the “found / not found” result.
Not every address gets one
When house-number matching did not succeed, when 3+3 is under maintenance or times out, or when 3+3 returns only 3 digits, no 6-digit code is stored. You can still save as normal, and the form still fills in the 3-digit postal code.
Restricted use
Chunghwa Post states that 3+3 lookup results are “for reference when writing mail addresses and for use by Chunghwa Post mail-processing units to sort mail only.” HowBridge uses it only for your recipient data and for no other purpose.
A 6-digit code does not guarantee faster delivery
A postal code is a code that makes mail sorting easier, and the benefit depends on how the processing side uses it. As early as 1987, the US audit agency found that among letters receiving the 9-digit postal code discount, only 10% were actually sorted automatically by machine.
The AddressNotServed field is not used yet
The AddressNotServed field in the test responses is not explained officially. HowBridge does not base any decision on it and will not block saving because of it.
Taiwan addresses only
3+3 covers Taiwan only; HowBridge also offers only China to Taiwan consolidation shipping, so all delivery addresses are in Taiwan.
Why do postal codes matter, and which studies can I consult?
The studies and reports below provide background. None of them is about HowBridge, and most of the figures come from the United States or other countries and cannot be applied directly to your parcel:
- Postal codes were originally meant to automate sorting: a report by the US Postal Service Inspector General says that before the ZIP Code was introduced in 1963, a letter was handled by an average of 8 to 10 postal workers; in 1983 it was extended to 9 digits (ZIP+4), and the report, citing a US audit agency estimate, says that 9 digits plus automation equipment would save US$5.26 billion over 16 years.
- Extra digits do not automatically make things faster: in 1987 the US audit agency reviewed 5 billion letters over 18 months that received the ZIP+4 postage discount, and only 10% were actually sorted by machine down to the carrier route; its 1995 report also noted that automation was progressing more slowly than expected.
- A postal code is a delivery code, not a patch of land: a 2006 study notes that postal codes are defined by the street addresses they serve and actually correspond to street segments; a 2002 study found that in the US about 390 postal codes were added and 120 retired between 1997 and 2001, so the postal service’s latest data should be used.
- If the address is wrong, automatic matching degrades sharply: a 2001 study gave 70 test addresses (50 containing errors) to 4 commercial geocoding companies, and accuracy ranged from 44% to 84%.
- Address problems are a visible cost: a US Postal Service Inspector General report says that in FY2014, 4.3% of mail could not be delivered as addressed, costing USPS nearly US$1.5 billion to handle and the mailing industry about US$20 billion a year; a Universal Postal Union white paper records that before Costa Rica introduced postal codes, 40% of the addresses in business customers’ databases were incorrect.
- Mail sorting in Taiwan is based on postal codes: a 2024 master’s thesis at National Central University used image recognition to read the postal code on letters and then sort them, and in the experiment postal code recognition accuracy was 95.24% and sorting accuracy was 94.49% (a laboratory prototype, not figures from Chunghwa Post’s actual equipment).
What do the common 3+3 postal code terms mean?
- 3+3 postal code
- The 6-digit postal code Chunghwa Post has used since 2020-03-03: the first 3 digits follow the administrative district in principle, and the last 3 digits are the delivery segment number.
- Delivery segment
- The delivery range shared by a run of house numbers on one road (for example odd numbers, even numbers, “and above”, “and below”); the last 3 digits of 3+3 are assigned by delivery segment.
- Bulk code
- Last 3 digits 201–799, used for places that receive bulk mail, such as government agencies, schools, companies, and buildings.
- 3+3 Postal Code Lookup Web Service
- A programming interface provided by Chunghwa Post that takes an address and returns a 6-digit postal code; it must be applied for on paper, with 1 fixed IP address registered.
- GetZipAddress
- One function of the 3+3 Web Service, returning a normalized address and the 6-digit postal code; this is the one HowBridge uses.
- SOAP
- A web service protocol that wraps requests and responses in XML; the 3+3 Web Service supports only SOAP.
- Non-address delivery
- Article 49 of the Mail Processing Rules: in hard-to-reach areas such as deep mountains and remote islands, Chunghwa Post may deliver without following the address and announces the delivery method.
- NSDA
- The Chunghwa Post National Standard Delivery Address platform, which returns a standard postal address and a 6-digit postal code; HowBridge has used it since 2026-09-23.
What are the sources and the scope of verification?
The sources below were consulted on 2026-10-06; document dates and consultation dates are shown separately, and no date is invented where none is stated.
Primary government and official sources
- Chunghwa Post: Postal code lookup (3+3 postal code lookup) | Document date: 2026-10-01; official wording on permitted use: “The 3+3 postal code lookup results of this system are for reference when writing mail addresses and for use by Chunghwa Post mail-processing units to sort mail only (please do not use them as a basis for writing addresses for other purposes).” Coding rules: “House numbers described as ‘and above’ or ‘and below’ include the stated number itself. ‘Odd’ means odd house numbers (lanes), ‘even’ means even house numbers (lanes), and ‘continuous’ includes both odd and even house numbers (lanes)”; where a “lane” is present, “the lane number should first be used to decide odd or even.” Military special mailboxes are “represented by the administrative district (township, town, city, district) number of the unit’s station plus ‘000’” (example 813000). The page also links the download of the “3+3 postal code lookup WebService system connection application form” and, with “please look it up on the National Standard Delivery Address platform”, links to NSDA. This shows that 3+3 is coded by delivery segment range, not by individual house number.
- Chunghwa Post: Delivery segment range usage notes | Document date: not stated; “Postal code last 3 digits 001–199 are the delivery range for ordinary residences, and 201–799 are bulk codes of bulk delivery segments, such as government agencies, schools, companies, and buildings (apartment complexes)”, for example 106216 National Taiwan University Post Office and 106319 National Taiwan University. Example of a delivery segment range: “Zhongzheng Road, even, Lane 206 and below” means all even house numbers or lane numbers from No. 2 through Lane 206 (including No. 206) belong to the same delivery segment range. The first 3 digits follow the administrative district in principle, but “to improve delivery efficiency, on some road sections Chunghwa Post uses first 3 digits that differ from the administrative district”; for example, Wugong Road and nearby sections in Xinzhuang District, New Taipei City are delivered by the Wugu post office and the first 3 digits become 248, and some road sections in Baoshan Township, Hsinchu County are assigned 300 instead of the district’s original 308.
- Government Open Data Platform: 3+3 postal code (dataset 150689) | Document date: 2026-06-01; providing agency “Chunghwa Post Co., Ltd.”, type api, license “Open Government Data License, version 1”, fee “free”, listed on 2022-03-07, metadata updated 2026-06-01. Remark: “to speed up mail sorting and help recipients receive their mail”, the new “3+3 postal code” system has been in effect since 2020-03-03. The resource description lists three documents: usage notes, the Web Service system connection application form, and the system interface specification.
- Chunghwa Post: 3+3 postal code System Interface Specification V1.0.3 | Document date: 2023-02-22; “Program type: Web Services”, service address https://33wsp.post.gov.tw/LZWZIP/TZIP33.asmx. GetZipCode “returns: String, six-digit postal code”, and returns the “normalized address” through an out parameter; GetZipAddress returns {"Address":"No. 216, Aiguo East Road, Da’an District, Taipei City","ZipCode":"106000"}; GetCityArea returns “county or city + township, town, city, or district” from a 3-digit postal code. Revision history: first edition 2019-10-21; from 2021-09-01 only HTTPS is open; V1.0.3 (2023-02-22) “disables TLS1.0 and TLS1.1 and allows only TLS 1.2 or higher connections.” Firewall destination IPs are 124.219.114.45, 124.219.115.45, and 203.69.145.45. The specification has no field for whether a house number exists or for a matching result, and has no AddressNotServed (0 occurrences in the full text).
- Chunghwa Post: TZIP33 Web Service WSDL | Document date: not stated; on 2026-10-06 the test returned HTTP 200 and 6,211 bytes, with the same SHA-256 as the copy archived on 2026-09-17. It defines only 3 operations (GetZipCode, GetCityArea, GetZipAddress), and the binding is only SOAP 1.1 and SOAP 1.2 (namespace http://tempuri.org/). The GetZipAddressResult type is string (a JSON string), so the fields inside the JSON do not appear in the WSDL; AddressNotServed cannot be found in either the WSDL or the asmx help page.
- Chunghwa Post: 3+3 Postal Code Lookup Web Service system connection application form | Document date: 2024-01-03; connecting IP “(1 group, fixed)”; signature “(non-individual applicants please stamp the organization seal and the responsible person’s seal)”. Note 1: “only 1 3+3 postal code can be queried per call”; note 2: “irregular system maintenance, about 2 to 3 hours each time, during which service is suspended”; note 3: for bulk lookups use the “3+3 postal code application system” conversion software; note 4: “this application form is in duplicate; after completing it, send it directly to the Mail Business Promotion Management Section of the Postal Service Department for review; after review it is passed to the Information Technology Department for system setup and testing ... the receiving unit returns one copy of the application form to the applicant”; note 5: “the applicant shall not use the returned information in any way harmful to Chunghwa Post and shall bear all losses and legal liability arising from that use”; note 6: contact mailbox ope01@mail.post.gov.tw. The form has no API key field, and records are kept for 5 years after termination of the application before being destroyed.
- Chunghwa Post: Usage notes for this company’s 3+3 postal code system | Document date: 2026-04-14; “Chunghwa Post updates the 3+3 postal code data on the first day of each quarter ... to ensure customers use the latest 3+3 postal code data and reduce mis-sorting of mail, the company has stopped providing 3+3 postal code data on its website and on the government open data platform.” The data file must be applied for through the file transfer management platform https://fpp.post.gov.tw/portal (business code zip, file transfer code zip33); the application form must be “stamped with your company’s seals and sent to our responsible unit for review. Download is allowed only after approval”; “customers should update regularly (every 3 months).” The date follows the one shown in the download area.
- Chunghwa Post Co., Ltd. “3+3 postal code” public license statement | Document date: 2020-10-22; “to speed up mail sorting and improve delivery efficiency, the 3+3 postal code data file was compiled”; “licensed on a royalty-free, non-exclusive basis, allowing users, without limit of territory, time, or number of uses ... to reproduce, and agreeing to the public display of 3+3 postal codes on any interface, provided this does not violate this company’s software terms of use, the laws of the Republic of China and/or other countries, or infringe the lawful rights of this company or third parties.” This is one of the licensing bases on which HowBridge uses and records 3+3 postal codes. The date follows the one shown in the download area.
- Chunghwa Post download area: Postal codes (including conversion software) | Document date: 2026-09-30; 17 items in total. The application form was updated on 2024-01-03, the specification on 2026-01-14, the public license statement on 2020-10-22, the 3+3 postal code application system (12.0MB) on 2026-09-30, the Taiwan area 3-digit postal code list on 2015-01-22, and the usage notes on 2026-04-14. All official 3+3 documents are downloaded from this page.
- Postal Act, Article 22 | Document date: 2023-06-28; “All mail shall be delivered according to the recipient’s address written on its surface. This does not apply to redirection, forwarding, or non-address delivery under Article 24 or under the rules set under Article 48.” Paragraph 2: “Mail that cannot be delivered shall be returned to the sender.” The date is the date the Postal Act was amended. The full text of the Postal Act does not contain the term “postal code”.
- Mail Processing Rules, Article 18 | Document date: 2022-05-27; “However, a discount may be given for bulk mail where the sender has written the postal code as required by Chunghwa Post and bundled the mail by district.” This is the only article in the Mail Processing Rules that mentions “postal code”; it concerns only the discount for bulk mailing and does not require ordinary senders to write a postal code. The date is the date the rules were amended.
- Mail Processing Rules, Article 43 | Document date: 2022-05-27; “Mail delivery areas are divided into address delivery areas and non-address delivery areas.” This shows that having a postal code does not mean delivery to the address is certain. The date is the date the rules were amended.
- Mail Processing Rules, Article 49 | Document date: 2022-05-27; “For mail to the following areas, Chunghwa Post may deliver without following the address and shall announce this: 1. Deep mountains. 2. Remote islands. 3. Areas with narrow footpaths of 2 kilometers or more that are not necessarily on a postal route. 4. Households or villages in remote areas that receive fewer than 40 pieces of mail a month on average. 5. Other special areas set by Chunghwa Post where delivery is clearly difficult because of poor transportation.” Paragraph 3: “The delivery method for non-address delivery mail shall be set and announced by Chunghwa Post.” The date is the date the rules were amended.
- Chunghwa Post: Non-address delivery area lookup | Document date: not stated; the official site announces non-address delivery ranges by county and city, with the columns “postal code / delivering post office / county or city / township or district / village / road or street / non-address delivery range”. Example: 114 Neihu Post Office Postal Service Section, Taipei City, Neihu District, Neigou Village, Dahu Street, “odd Nos. １４１ to １４３”; Taipei City has 15 entries in total. Chunghwa Post does not explain how this list relates to the 3+3 response fields.
- Chunghwa Post: National Standard Delivery Address platform (standard postal address conversion and Web API) | Document date: not stated; the Chunghwa Post 3+3 lookup page links to this platform with “please look it up on the National Standard Delivery Address platform”. Platform FAQ: “users can query standard postal addresses through an API; 2 APIs are currently provided, and this function is currently available to registered members.” The API GetPostAddrNo (launched 2020-11-19) “takes an address and returns that address’s postal code, standard postal address, address code, and other content”; isStandard: “enter 1 if matching against the postal addresses on record at Chunghwa Post is needed (if the address is not on record, an empty address code is returned)”; APIKey: “because the service is limited to members and bound to an IP.”
Research literature and international reports
The Untold Story of the ZIP Code (Report No. RARC-WP-13-006)
US Postal Service Inspector General report: the ZIP Code was introduced in 1963 to make mail sorting automatable; before ZIP Codes and automated sorting, a letter was handled by an average of 8 to 10 postal workers. In 1983 it was extended to 9 digits (ZIP + 4), where the extra 4 digits can point to one side of a street or one office building; the report cites a 1983 GAO estimate that 9 digits plus new automation equipment would save the postal service and mailers US$5.26 billion over 16 years, and it was later extended to 11 digits to sequence the carrier’s delivery order. The report also estimates that ZIP Codes bring the US economy nearly US$10 billion in value each year (the authors describe this as a rough estimate).
Postal Service's Processing of ZIP + 4 Letters Receiving Postage Discounts (T-GGD-88-1)
GAO reviewed 5 billion letters over 18 months that received the ZIP + 4 postage discount: only 10 percent were actually sorted by machine down to the carrier route, and USPS therefore gave about US$25 million in discounts for mail that was not automatically sorted; automation had been planned for about 215 processing centers, but only 130 were completed in fiscal year 1986. It shows that extra digits become sorting efficiency only when the processing side has the equipment and procedures to match.
Postal Service: Automation Is Taking Longer and Producing Less Than Expected (GAO/GGD-95-89BR)
USPS aimed to barcode nearly all mail by the end of fiscal year 1995 (about 90 percent of more than 115 billion letters a year); the 1993 baseline was 80 billion letters, of which 60 billion were actually barcoded jointly by the postal service and mailers; the automation program involved up to about 14,000 pieces of equipment and about US$5 billion. It likewise shows that postal codes and barcodes are the precondition for automated sorting, but the benefit depends on execution.
Addressing the world – An address for everyone (White paper)
The UPU (Universal Postal Union) white paper says address standards can “facilitate mail handling (automatic sorting, distribution)”. In the Costa Rica case, one purpose of the postal code system was to help divide, sort, and distribute mail to shorten delivery time and reduce address errors; before its introduction, postal research found that 40% of the addresses in business customers’ databases were incorrect and that only 20% of the daily mail in the capital’s metropolitan area reached its destination, and a preliminary study estimated annual losses of US$720 million for the country.
Undeliverable as Addressed Mail (Report No. MS-AR-14-006)
In FY2013 the US Postal Service handled more than 158 billion pieces of mail, and nearly 6.8 billion pieces (4.3 percent) could not be delivered as addressed (UAA), at an estimated handling cost of US$1.5 billion; causes include moves, illegible addresses, and deceased recipients; USPS automatically sampled the address accuracy of only 3 percent of mail. It shows that address problems are a quantifiable system cost (this figure covers all address problems, not postal codes alone).
Management Advisory – Strategies for Reducing Undeliverable as Addressed Mail (Report No. MS-MA-15-006)
In FY2014 more than 155 billion pieces were handled, of which 6.6 billion (4.3 percent) were UAA; USPS spent nearly US$1.5 billion and the mailing industry about US$20 billion a year. According to a 2006 study, about 40 percent of UAA originated with the public, 35 percent with mailing businesses (such as address lists that were not updated), and about 23 percent with the postal service’s own sorting errors or failed deliveries. It supports having senders get their address data right at the source.
On the use of ZIP codes and ZIP code tabulation areas (ZCTAs) for the spatial analysis of epidemiological data
Although postal codes are often drawn as polygon areas, in practice they are defined by the street addresses they serve and correspond to “linear features (street segments)”, so treating them as continuous areas imposes a structure that does not exist; carrier routes are often adjusted, and postal codes are split, retired, or added. New York State’s ZCTA file has 851 more polygons than its postal code map. It supports the point that a postal code is a delivery code and cannot be used to judge whether a house number exists.
Zip Code Caveat: Bias Due to Spatiotemporal Mismatches Between Zip Codes and US Census–Defined Geographic Areas—The Public Health Disparities Geocoding Project
A postal code is an administrative unit that USPS sets up to deliver mail as efficiently as possible, and it usually does not follow administrative or statistical boundaries; from 1997 to 2001 about 390 postal codes were added and 120 retired in the US; of 166,730 cancer cases in Massachusetts, 17,376 (10.4%) were assigned to 193 postal codes that did not exist in the 1990 census. It shows that postal codes change with delivery needs, so the postal service’s latest data must be used.
On the wrong side of the tracts? Evaluating the accuracy of geocoding in public health research
The study gave 70 test addresses (50 of them containing errors) to 4 commercial geocoding companies, and accuracy ranged from 44% (95% CI 32%–56%) to 84% (95% CI 73%–92%); the best company’s accuracy on real addresses from a public health database was 96%. It shows that once an address contains an error, the result of automatic matching drops sharply, which is why HowBridge adds a 6-digit code only when house-number matching succeeded.
Automatic Recognition and Sorting System for Bill-Type Letters (in Chinese; English title translated)
A Taiwan master’s thesis: image recognition reads the postal code on bill-type letters, and a six-axis robotic arm then places them into the matching sorting bins; in the experiment, postal code recognition accuracy was 95.24% and overall correct sorting rate was 94.49%, and it cites the Chunghwa Post postal statistics yearbook. It supports the point that mail sorting in Taiwan is based on postal codes; however, the abstract does not say whether 3+3 or 3+2 codes were tested, and the figures are not from Chunghwa Post’s actual sorting machines.
The process reflects the HowBridge server program as of 2026-10-06; the test results are 12 direct calls made that day and do not represent all addresses. Chunghwa Post has not published an explanation of the AddressNotServed field, nor statistics on delays caused by wrong postal codes, and this page draws no inference about them. The exact date on which Chunghwa Post approved the connection application is as stated in the official notice; this page states only the date the connection was confirmed working.
Frequently asked questions about 3+3 postal code completion
Does HowBridge connect to the Chunghwa Post 3+3 postal code service?
Does this mean Chunghwa Post certifies or endorses HowBridge?
Can 3+3 tell whether an address is correct?
Do I need to enter the 6-digit postal code myself?
Why was my delivery address not given a 6-digit code?
Where can I see the 6-digit postal code?
Are my name and phone number sent to Chunghwa Post?
If I write the 6-digit postal code, will my parcel arrive sooner?
What is AddressNotServed in the response?
Are convenience store pickup addresses also given a 6-digit code?
Further reading
Chunghwa Post NSDA: postal verification of delivery addresses
TGOS house-number matching: HowBridge obtains Ministry of the Interior TGOS usage approval
HowBridge connects to Ministry of the Interior TGOS coordinate-to-house-number: fill in a delivery address from your current location
Will a wrong delivery address cause a return? How to fix it and how to avoid it
HowBridge LINE Official Account guide
Privacy Policy
Enter and verify your delivery address first
Go to the Member Center to add or confirm your Taiwan home delivery address; once house-number matching succeeds, the system adds the 6-digit postal code automatically.
Enter a delivery address in the Member Center