How is the Paraguayan RUC check digit calculated?

The SET uses a modulo-11 with a cycling multiplier. Reading the base from right to left, each digit is multiplied by an increasing factor starting at 2, and the factor resets to 2 after it reaches 11. The products are summed, the remainder modulo 11 is taken, and the check digit is 11 minus that remainder, with any result of 10 or 11 collapsing to 0.

Can I compute the check digit from the base?

Yes. If you enter only the base number without a check digit, the tool computes and displays the correct DV and the full RUC, which is useful when registering a new number.

Does a valid RUC mean the taxpayer is registered?

No. A valid result confirms the RUC passes the SET check-digit rule and is internally consistent. It does not confirm the taxpayer is registered or active. Confirm status on the official SET portal before issuing electronic invoices.

Why does my RUC fail?

Most failures are a mistyped or transposed digit, or a wrong check digit. Because the check digit depends on the whole base, a single wrong digit breaks the result. The tool shows the expected DV so you can spot the mistake.

Is my RUC sent anywhere?

No. The cycling-multiplier maths runs entirely in your browser. Nothing is uploaded, which makes it safe to validate supplier and customer records in bulk.

Paraguay RUC Validator

The RUC (Registro Único de Contribuyentes) is Paraguay’s tax identifier, administered by the SET (Subsecretaría de Estado de Tributación). It is written as a base number followed by a single check digit (DV), for example 80012345-6. This free validator computes and verifies the DV using the SET’s modulo-11 algorithm.

How it works

The SET uses a weighted modulo 11 with a cycling multiplier:

Read the base digits from right to left.
Multiply each digit by an increasing factor that starts at 2; once the factor passes 11, reset it to 2 and continue.
Sum the products.
Compute sum mod 11.
The check digit is 11 - remainder. If that yields 10 or 11, the check digit collapses to 0.

If you supply the check digit, the tool verifies it. If you supply only the base, it computes and shows the correct DV and the full RUC string.

Example and notes

For base 80012345, the algorithm weights the digits right to left with the cycling factor, sums them, and derives the check digit. The tool then reports the full RUC as 80012345-DV and, if you entered a DV, whether it matches.

A valid result confirms the RUC is internally consistent under the SET rule — it does not confirm the taxpayer is registered or active. For SIFEN (electronic invoice) compliance, confirm status on the official SET portal. All processing is local; your RUC never leaves your device.