What is a Slovenian DDV-ID?

DDV is the Slovenian abbreviation for Davek na dodano vrednost (Value Added Tax). The DDV identification number, or DDV-ID, is issued by FURS (the Financial Administration of Slovenia) to VAT-registered businesses. It consists of the country prefix SI followed by an 8-digit davčna številka (tax number).

How does the modulo-11 check digit work?

The first seven digits are multiplied by the fixed weights 8, 7, 6, 5, 4, 3, 2 respectively. The weighted products are summed, and the remainder of that sum divided by 11 is computed. The check digit is 11 minus that remainder. If the result is 10 the number is invalid, and if it is 11 the check digit is 0.

Is the SI prefix required?

The SI prefix is part of the EU VAT identifier used for intra-community transactions, but the underlying tax number is just the 8 digits. This tool accepts the number with or without the SI prefix and validates the 8-digit core either way.

Does a valid check digit prove the company exists?

No. A valid check digit only proves the number is mathematically well-formed and free of common transcription errors. To confirm a business is actually VAT-registered and active, check the EU VIES system or the Slovenian business register.

Is my VAT number sent anywhere?

No. All validation runs in JavaScript inside your browser. Nothing is uploaded, logged, or stored. You can go offline before entering the number and the tool still works.

Slovenia DDV-ID Validator

Slovenian DDV-ID at a glance

The DDV-ID is Slovenia’s VAT identification number, issued by FURS (Finančna uprava Republike Slovenije). For cross-border EU use it is written as the prefix SI followed by an 8-digit davčna številka (tax number) — for example SI12345679. The eighth digit is a check digit computed from the first seven using a weighted modulo-11 algorithm, which lets you catch typos before submitting an eDavki VAT filing.

How it works

The check digit uses a fixed weight vector applied to the first seven digits:

weights = [8, 7, 6, 5, 4, 3, 2]
sum     = Σ (digit[i] * weight[i])   for i = 0..6
rem     = sum mod 11
check   = 11 - rem
  if check == 10 → number is INVALID
  if check == 11 → check = 0

The computed check must equal the eighth digit. This scheme detects all single-digit substitution errors and most adjacent transpositions. The first digit cannot be 0, since valid tax numbers do not begin with a leading zero.

Tips and example

Take 15012557. Weighted sum = 1·8 + 5·7 + 0·6 + 1·5 + 2·4 + 5·3 + 5·2 = 8 + 35 + 0 + 5 + 8 + 15 + 10 = 81. 81 mod 11 = 4, so check = 11 − 4 = 7. The eighth digit is 7, so the number is valid. Remember that a correct check digit only guarantees the number is well-formed — use VIES to confirm the registration is real and active.