What is a Taiwan National ID number?

The Republic of China (ROC) National Identity Card number (國民身份證統一編號) is a 10-character identifier issued to all ROC citizens. It consists of one uppercase letter indicating the district where the ID was first registered, followed by nine digits. The second digit encodes gender (1 = male, 2 = female) and the final digit is a checksum computed by the Ministry of Interior algorithm.

How does the Taiwan ID checksum work?

The leading letter maps to a number from 10 (A) to 35 (Z). Its tens digit is multiplied by 1 and its units digit by 9. The next eight digits are multiplied by weights 8, 7, 6, 5, 4, 3, 2, 1 in order. All products are summed, and the check digit (position 10) must make the grand total divisible by 10 — i.e., check = (10 − (sum mod 10)) mod 10.

What does the leading letter mean?

The letter encodes the district office that issued the ID — historically the county or city where the holder was registered. Common codes include A (Taipei City), B (Taichung City), F (New Taipei City), H (Taoyuan City), and E (Kaohsiung City). There are 26 codes in total (A–Z), covering all municipalities, counties, and special administrative areas of Taiwan.

What does the second digit mean?

The second character is always 1 or 2. A 1 means the holder is male; a 2 means female. Any other value immediately makes the ID structurally invalid. This gender digit is part of both the format check and the weighted checksum calculation.

Does a valid checksum mean the ID is registered to a real person?

No. Checksum validation only confirms internal mathematical consistency — it cannot tell you whether the number is assigned to a living person in the National Household Registration database. A number can pass all structural tests and still be unassigned, cancelled, or belong to a deceased holder. This tool is purely a format and arithmetic checker.

Are foreign resident IDs the same format?

No. The Alien Resident Certificate (ARC) and Taiwanese American Resident Certificate (TARC) use a similar 10-character structure but the second digit is 8 or 9 instead of 1 or 2. This tool validates the citizen format only; entering an ARC number will report an invalid gender digit.

Taiwan National ID Validator

Taiwan’s National Identity Card (國民身份證, guómín shēnfèn zhèng) is the primary government-issued identifier for all Republic of China citizens. The card number is a 10-character string printed on the front of every ROC ID card and used across government portals, bank account applications, healthcare systems, tax filings, and any process requiring verified identity in Taiwan. This validator checks the number’s full internal structure — format, gender digit, and the official Ministry of Interior checksum — in your browser, with no data uploaded anywhere.

What the 10 characters mean

A valid Taiwan National ID looks like A123456789 (a clearly fake example — every real number must pass the checksum). Each section carries specific information:

Position	Content	Example
1	Issuance district letter (A–Z)	A = Taipei City
2	Gender digit (1 = male, 2 = female)	1
3–9	7-digit serial (region sequence)	2345678
10	Weighted check digit	9

The letter in position 1 was assigned when the ID was first issued and reflects the household registration district at that time — someone with an “A” prefix originally registered in Taipei City, even if they have since moved elsewhere. Common prefixes include A (Taipei City), B (Taichung City), E (Kaohsiung City), F (New Taipei City), and H (Taoyuan City).

How the checksum is computed

The ROC Ministry of Interior uses a weighted digit-sum algorithm:

Map the letter to a two-digit value: A = 10, B = 11, … Z = 35.
Split that value: tens digit (always 1) is weighted ×1; units digit is weighted ×9.
Weight the body digits at positions 2–9 with descending weights 8, 7, 6, 5, 4, 3, 2, 1.
Sum all nine weighted products.
Compute the check digit: (10 − (sum mod 10)) mod 10.
The final character (position 10) must equal this computed check digit.

Worked example

Take the fictional ID A234567890 (deliberately constructed to show the arithmetic):

A → 10; tens digit 1 × 1 = 1; units digit 0 × 9 = 0
2 × 8 = 16, 3 × 7 = 21, 4 × 6 = 24, 5 × 5 = 25, 6 × 4 = 24, 7 × 3 = 21, 8 × 2 = 16, 9 × 1 = 9
Sum = 1 + 0 + 16 + 21 + 24 + 25 + 24 + 21 + 16 + 9 = 157
Check digit = (10 − (157 mod 10)) mod 10 = (10 − 7) mod 10 = 3
The number above ends in 0, not 3, so it would fail the checksum.

The tool performs exactly this arithmetic instantly for any ID you enter.

Formula note

The algorithm is a straightforward mod-10 weighted checksum, not a cryptographic hash. It was designed to catch single-digit transcription errors and most transpositions but is not collision-resistant. Because the full letter-to-weight mapping and the weights are published in government standards, it is possible to construct numbers that pass the check but are not genuine government-issued IDs — validation here is strictly mathematical. The only authoritative source for whether a number is genuinely registered is the Ministry of the Interior’s National Household Registration database, which is not publicly queryable.