Taiwan National ID and resident certificate number validator. 1 letter + 9 digits with a check digit; old two-letter resident numbers too. Browser-only — your ID never leaves the page.
Taiwan National ID Format Validator (台灣身分證)
How to use
Enter the number
1 letter + 9 digits, e.g. A123456789. Spaces, hyphens and full-width characters are fine. An old-format resident certificate number has 2 letters + 8 digits.
Letter → 2-digit code
Each letter becomes a code from 10 to 35, not in alphabetical order: A=10 … H=17, then J=18 … V=29, then X=30, Y=31, W=32, Z=33, I=34 and O=35. None of the codes from 10 to 35 is skipped.
Weighted sum
Apply weights [1,9,8,7,6,5,4,3,2,1,1] to the 2-digit letter code + 9 digits. On an old-format number the second letter counts as the last digit of its code.
Mod 10 check
The sum must be divisible by 10 for VALID. The 2nd character is the sex code: 1 = male, 2 = female for citizens; 8 = male, 9 = female on resident certificate numbers issued since 2021 (A and C male, B and D female on the old format).
About the Taiwan National ID number
Taiwan's National ID number is 1 letter + 9 digits. A Ministry of the Interior regulation sets out its structure (國民身分證及戶口名簿格式內容製發相片影像檔建置管理辦法, Article 3): the letter stands for a special municipality, county or city, the 2nd character is the sex code, and the 10th is the check digit. The seven digits in between are a serial, which the Ministry says carries no meaning. For a citizen the letter records where the number was first assigned, and it does not change if you move.
26 letters: 22 current divisions and 4 that are gone
A=Taipei City, B=Taichung City, C=Keelung City, D=Tainan City, E=Kaohsiung City, F=New Taipei City, G=Yilan County, H=Taoyuan City, I=Chiayi City, J=Hsinchu County, K=Miaoli County, M=Nantou County, N=Changhua County, O=Hsinchu City, P=Yunlin County, Q=Chiayi County, T=Pingtung County, U=Hualien County, V=Taitung County, W=Kinmen County, X=Penghu County, Z=Lienchiang County. L, R, S and Y name units that no longer exist: Taichung, Tainan and Kaohsiung counties (merged into their cities on 25 December 2010) and Yangmingshan. Numbers already issued under them stay valid. Our guide to Taiwan's 22 counties and cities has the full table and its history.
"Ten characters in four parts: the letter, the sex code, a seven-digit serial and the check digit."
What the check digit catches, and what it misses
The check rule was printed in full in the Executive Yuan Gazette in 2009, in a National Health Insurance claim-file specification. We ran every possible error through this tool's rule. A wrong digit anywhere in characters 2 to 10 slips through in 80 of 810 cases, about 1 in 10, and every swap of the last two digits passes, because both carry weight 1. Every other swap of neighbouring digits is caught. So VALID means the format is right, not that the number was typed correctly.
Resident certificate numbers (統一證號)
Since 2 January 2021 the National Immigration Agency has issued resident certificate numbers in the same layout, with 8 (male) or 9 (female) as the 2nd character. They go to foreign nationals, nationals without household registration, and residents of Hong Kong, Macau and the mainland. On these numbers the letter is the place of application, not a place of origin. Numbers issued earlier have 2 letters + 8 digits; they can be exchanged until 31 December 2030 and stop being used on 1 January 2031. This tool checks both formats.
Privacy stance
This tool runs entirely in your browser; the number is never uploaded, logged, or stored. Taiwan's Personal Data Protection Act lists the national ID number as personal data in Article 2. It is not one of the Article 6 special categories (medical records, medical care, genetics, sex life, health checks and criminal records), but the Act still protects it. Since 2014 the National Development Council has told government agencies to mask the last 4 characters. Because the check digit is fixed by the rest, only 1,000 of the 10,000 ways to fill those four stars pass the check, so the mask hides three digits' worth, not four.
The letter records where it was first issued, and never changes
Taiwan first issued National ID Cards in May 1947. Since July 1969 the unified number has been assigned at birth registration.
The check digit comes from a public weighted-sum rule, printed in full in the Executive Yuan Gazette in 2009, so the format can be verified entirely offline.
For a citizen the letter reflects where the number was first assigned, and it doesn't change if you move later. On a resident certificate number it is the place of application.
L, R and S belonged to Taichung, Tainan and Kaohsiung counties, which merged into their cities on 25 December 2010. Numbers already issued under those letters stay valid. I (Chiayi City) and O (Hsinchu City) are current cities.
The sex code is the 1st digit after the letter: 1 = male, 2 = female for citizens, 8 and 9 on resident certificate numbers. A number is meant to last for life, but registering a change of sex means the household registration office assigns a new number.
Only the letter, the sex code and the 7 serial digits vary: 26 × 2 × 10⁷ = 520 million possible citizen numbers. The check digit adds none.
The "New eID" digital ID card was due in 2021, but the Executive Yuan suspended it on 21 January 2021. On 31 July 2024 the Ministry of the Interior said it would move again only once the Personal Data Protection Commission is set up, and the provision creating that commission has no commencement date yet. The current card and its number remain in use.
Since 2 January 2021, the new-format resident certificate number follows the ID card layout: 1 letter + 9 digits, with 8 = male and 9 = female in 2nd position. It is issued to foreign nationals, nationals without household registration, and residents of Hong Kong, Macau and the mainland. The old format (2 letters + 8 digits) stops being used on 1 January 2031.
Taiwan's Article 6 special categories are only medical records, medical care, genetics, sex life, health checks and criminal records — the national ID is ordinary personal data under Article 2.
Frequently Asked Questions
No. Validation runs entirely in your browser — your ID is never uploaded, logged, or stored.
No. It only means the number satisfies the format and checksum rules; it cannot show that the number was ever issued, or to whom. The Ministry of the Interior runs an online check of card issue records, 國民身分證領補換資料查詢, which needs the card's issue details; for resident certificate numbers the National Immigration Agency runs 新舊統一證號申請結果查詢.
For a citizen, the special municipality, county or city where the number was first assigned, e.g. A = Taipei City, E = Kaohsiung City, F = New Taipei City. It doesn't change if you later move. On a resident certificate number the letter is the place of application.
They name units that no longer exist: L = Taichung County, R = Tainan County, S = Kaohsiung County (all merged into their cities on 25 December 2010) and Y = Yangmingshan. Numbers starting with these letters are still valid. I (Chiayi City) and O (Hsinchu City) are current cities.
Yes, both formats. The new-format resident certificate number, issued since 2 January 2021, follows the ID card layout with 8 (male) or 9 (female) as the 1st digit. It is issued to foreign nationals, nationals without household registration, and residents of Hong Kong, Macau and the mainland. Older numbers (2 letters + 8 digits, second letter A, B, C or D) are checked with the same rule, the second letter counting as the last digit of its code; the National Immigration Agency says they stop being used on 1 January 2031.
Yes, from the 2nd character: 1 = male, 2 = female for citizens, and 8 = male, 9 = female on resident certificate numbers issued since 2021. Registering a change of sex means a new number is assigned (Taipei City Zhongzheng District Household Registration Office).
No. Taiwan IDs do not encode birth date (unlike Mainland China). Age requires separate household register lookup.
New eID is not being issued. The Executive Yuan suspended it on 21 January 2021, and on 31 July 2024 the Ministry of the Interior said it would move again only once the Personal Data Protection Commission is set up; the provision creating that commission has no commencement date yet. Your current card and number remain in use.
This page validates one at a time for privacy. For bulk use, copy the JavaScript algorithm into your own code (no API required).
Yes. All RECATOOLS tools are 100% free, ad-supported. No signup, no paywall.
Method & sources
How it computes
One letter and nine digits. The letter maps to a two-digit code from 10 to 35, none skipped but not in alphabetical order (I = 34, O = 35, W = 32, X = 30, Y = 31, Z = 33); weights 1, 9 on that code and 8, 7, 6, 5, 4, 3, 2, 1, 1 on the digits; valid when the sum is divisible by 10. An old-format resident certificate number (two letters + eight digits, issued before 2 January 2021) uses the same rule with the second letter counted as the last digit of its code.
What this tool implements
- Second digit is the sex code: 1 = male and 2 = female for citizens; 8 = male and 9 = female on the resident certificate number (統一證號) issued since 2 January 2021 to foreign nationals, nationals without household registration, and residents of Hong Kong, Macau and the mainland (National Immigration Agency). On a resident number the letter is the place of application.
- The 2021 resident number deliberately copies the ID-card layout, so the same checksum applies. Old two-letter numbers (second letter A/B or C/D) use the same rule with the second letter counted as the last digit of its code, as the 2009 Executive Yuan Gazette prints; they can be exchanged until 31 December 2030 and stop being used on 1 January 2031, and this tool checks them.
- The weighted-sum rule is public: the Executive Yuan Gazette printed it in full in 2009, with the worked example A123456789, which this tool reproduces. No Ministry of the Interior or National Immigration Agency page checked sets it out; the Agency's own Q&A names the 10th digit only as the check code.
Sources
- National Immigration Agency (Taiwan). 外來人口統一證號 — Q&A (format: 1 letter + 9 digits, 8 = male, 9 = female). https://www.immigration.gov.tw/5385/12162/238449/CP_QA?alias=QACl…
- National Immigration Agency (Taiwan), 新住民全球新聞網. 新式外來人口統一證號換發介紹 (from 2 January 2021). https://news.immigration.gov.tw/EasyPack/Detail/6fa938aa-2427-423…
- Executive Yuan Gazette (行政院公報), vol. 15 no. 149, 5 August 2009, Health and Labour section, p. 23808: Bureau of National Health Insurance announcement 健保醫字第0980091115號 (31 July 2009), attachment 住院醫療服務點數清單媒體申報格式及填表說明, which prints 「檢查號碼計算規則」 in full — the leading letter converted to two digits, each digit multiplied by 1987654321, the units digits summed, and the check digit 10 minus the last digit (0 when it is 0) — with the worked example A123456789. https://gazette.nat.gov.tw/EG_FileManager/eguploadpub/eg015149/ch…
- Ministry of the Interior (Taiwan). 國民身分證及戶口名簿格式內容製發相片影像檔建置管理辦法, Article 3 (amended 18 October 2024): the unified number is ten characters, the first a letter for the special municipality, county or city, the second the sex code and the tenth the check code. https://law.moj.gov.tw/LawClass/LawAll.aspx?pcode=D0030030
- National Immigration Agency (Taiwan). 統一證號與國民身分證字號有無差異? (Q&A, updated 3 December 2024): the unified number is used by foreign nationals, nationals without household registration, Hong Kong and Macau residents and mainland residents; the new format since 2 January 2021 is one letter + nine digits with 8 = male and 9 = female. https://www.immigration.gov.tw/5385/12162/238449/382804/
- National Immigration Agency (Taiwan). 請問舊式統號會停止使用嗎? (Q&A, 6 February 2023): old-format numbers can be exchanged from 2 January 2021 to 31 December 2030 and stop being used on 1 January 2031. https://www.immigration.gov.tw/5385/12162/238449/243723/
- National Development Council (Taiwan). Letter 發資字第1031501471號, 31 December 2014: agencies mask the last four characters of a national ID number with *. https://security.ndhu.edu.tw/var/file/102/1102/img/2680/30463647.pdf
- Taipei City Zhongzheng District Household Registration Office. 性別變更登記 (Q1: a change of sex is registered by assigning a new unified number). https://zzhr.gov.taipei/cp.aspx?n=703A72BF52DE9F09
Abridged — the full review record for this tool runs longer than the list above.
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