What a Chilean RUT is and how the check digit works
The RUT (Rol Único Tributario) is Chile’s tax identification number for both individuals and companies. For individuals it matches the RUN, the national ID number printed on the identity card. A RUT has two parts: a body of up to eight digits and a check digit (called dígito verificador or DV) after a dash. The check digit can be a number from 0 to 9 or the letter K, so a full RUT looks like 12.345.678-5.
That last character is not random. It is derived from the body using the module 11 algorithm, which means a single mistyped digit makes the whole number fail validation. Any form or system can catch typos instantly without looking anything up in a database — and that is exactly what this tool does, entirely in your browser.
How to use this tool
There are two modes:
- Validate a full RUT: paste the complete number, with or without dots and the dash (
12.345.678-5,12345678-5and123456785all work). The tool tells you whether it is valid and, if it is not, which check digit the body should have. - Compute the check digit: type only the body (the digits before the dash) and the tool returns the DV plus the properly formatted RUT with dots and a dash, ready to copy.
The module 11 algorithm, step by step
- Take the digits of the body from right to left.
- Multiply each one by the sequence
2, 3, 4, 5, 6, 7; when the sequence runs out, start again at 2 (it cycles). - Add up all the products.
- Divide the sum by 11 and keep the remainder.
- The check digit is
11 − remainder, with two special cases: a result of 11 becomes0, and a result of 10 becomes the letterK.
Worked example
Let’s compute the check digit for the body 12,345,678. Reading the digits right to left and applying the cycling sequence:
| Digit (right → left) | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
|---|---|---|---|---|---|---|---|---|
| Multiplier | 2 | 3 | 4 | 5 | 6 | 7 | 2 | 3 |
| Product | 16 | 21 | 24 | 25 | 24 | 21 | 4 | 3 |
The products add up to 138. Dividing by 11 leaves a remainder of 6 (11 × 12 = 132), so the check digit is 11 − 6 = 5 and the full RUT is 12.345.678-5.
Another case: the body 11.111.111 gives 1 × (2+3+4+5+6+7+2+3) = 32, the remainder of 32 ÷ 11 is 10, and 11 − 10 = 1, so the valid RUT is 11.111.111-1. When the remainder is 1 the subtraction yields 10 and the DV becomes the letter K — for instance 20.780.004-K.
Frequently asked questions
Is this a “rutificador”? Can I look up a person by their RUT?
No. A rutificador searches databases for the personal data linked to a RUT. This page does nothing of the sort: it only applies the module 11 formula to the digits you type. It never queries Chile’s Civil Registry, the SII tax authority or any other records, and nothing you enter leaves your browser.
What does the letter K mean in a RUT?
It is simply the check digit assigned when 11 − remainder equals exactly 10. Since the DV must fit in a single character, Chilean convention uses K instead of writing “10”. It says nothing special about the holder — it is just one of the eleven possible outcomes of the algorithm.
What is the difference between RUT and RUN?
The RUN is the national identity number of natural persons (the one on the ID card), while the RUT is the tax roll number. For individuals both numbers are identical. Companies and other legal entities only have a RUT, typically issued in ranges above 50 million.
If a RUT validates, does that mean it exists and belongs to someone?
Not necessarily. A matching check digit only proves the number is mathematically consistent; it does not confirm that the number has actually been issued to a real person or company. For any formal procedure, identity verification is up to the Civil Registry or the SII.
Why does a RUT I know is correct show as invalid?
Almost always a typo: one digit swapped, one digit missing or extra, or a K typed as a zero. Compare the number against the original document — the tool shows you the check digit that would match the body you entered, which usually reveals where the difference is.