Iranian national ID validator

The national ID has ten digits in three parts:

• First three digits: the place-of-issue code, i.e. the county or office where the code was issued.
• Next six digits: the person's unique number within that office.
• Tenth digit: a check digit calculated from the first nine, which exposes typos.

The place-of-issue code is not necessarily the place of birth or residence; it is where the code was issued. So you cannot reliably infer someone's city from the first three digits, and this tool does not try.

1. 1

   Multiply by the weights

   Multiply the first nine digits, from the left, by 10, 9, 8, 7, 6, 5, 4, 3 and 2.

2. 2

   Add the products

   Add the nine products together.

3. 3

   Remainder mod 11

   Take the remainder of that sum divided by 11.

4. 4

   Compare with the tenth digit

   If the remainder is less than 2, the tenth digit must equal the remainder; otherwise it must equal 11 minus the remainder.

Only about one in ten random 10-digit numbers passes this test. Most single-digit typos and swaps of two adjacent digits also break the check digit. Still, a valid code only means the structure is correct, not that the code actually belongs to someone.

Many people's national IDs, including most of those issued in Tehran, start with a zero and sometimes two. These zeros are part of the place-of-issue code, and a code with leading zeros is just as valid as any other.

Trouble starts when the national ID is treated as a number. Excel strips leading zeros and shows 0012345679 as 12345679; the code becomes eight digits and fails every check. This tool pads eight- and nine-digit codes with zeros and warns you, because that is almost always what happened to them.

To prevent it, set the column format to Text in Excel before entering the codes (Format Cells, then Text). If the codes are already damaged, restore them to ten digits with =TEXT(A2,"0000000000").

Common mistakes in designing a national ID field are explained in the post What does a national ID starting with zero mean? Validating it correctly in forms.

If you have a registration list, a payroll sheet or a form export, copy the national ID column from Excel and paste it into Bulk check. Each line is checked separately and the line order, including empty lines, is preserved. Copy the result column and paste it next to the original column in Excel to filter the problem rows. Duplicate codes are counted separately.

The best place to check a national ID is the moment it is entered, not weeks later in Excel. The National ID field in Porsino's form builder runs this same algorithm while the form is being filled in:

• It accepts Persian and Arabic digits and stores them in a single format.
• It keeps the code as text, so the leading zero is never lost.
• It rejects an invalid code before submission, and the same check runs again on the server so it cannot be bypassed by tampering with the browser.
• If each person may respond only once, set "One response per code" to the national ID question in the share settings, so the same code cannot be submitted twice from any device.

To build a registration form with a national ID, see Online registration form for details.