Reference number calculator

Make or check an Estonian or Finnish reference number (7-3-1), a Belgian structured communication or a Slovenian SI reference.

Payment & FeesBusiness

Country

Task

Invoice or customer number

Type a number. The answer appears here as you type.

Results are informational. Calculation is based on your input and public rules, official accounting may differ. For accuracy, confirm the final result if needed from the appropriate official source or specialist. See the terms of use.

How it works?

A reference number ties a payment to its invoice: the payer writes it on the transfer and the payee sees at once which invoice was paid. Its last digit is a check digit computed from the others, so a typo is caught: a bank does not accept a reference whose check digit is wrong.

Estonia and Finland use the same 7-3-1 method: the digits are multiplied from right to left by the weights 7, 3, 1, 7, 3, 1 and so on, the products are added up and the sum is taken from the next full ten. The difference is the check digit (0 instead of 10). An Estonian reference has 2 to 20 digits, a Finnish one 4 to 20. In Finland it is printed in groups of five from the right and without leading zeros, for example "12 34561".

The Belgian structured communication (gestructureerde mededeling, communication structurée) is 12 digits written +++010/8068/17183+++. The last two digits are the remainder of the first ten divided by 97, and a remainder of 0 is written 97.

The Slovenian reference (sklic) goes on the UPN payment order: SI, a two-digit model and up to three numbers joined by hyphens, for example SI05 19-1235-84503. The model says which part ends in a check digit. It is computed modulo 11 with the weights 2, 3, 4 and so on from the right.

Every reference is also shown in its RF form (ISO 11649), the common reference of SEPA payments that banks in other countries know too.

Frequently asked questions

How is the check digit of a reference number computed?

The check digit of an Estonian or Finnish reference comes from the 7-3-1 method. The Estonian Banking Association's example: base 12131295. The weights from right to left are 7, 3, 1, 7, 3, 1, 7, 3, so the products add up to 98. The next full ten is 100 and 100 - 98 = 2, so the reference is 121312952. When the sum already is a full ten, the check digit is 0. The calculator's "Check" task does the same the other way round and tells you whether the last digit fits.

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What is the difference between an Estonian and a Finnish reference number?

The check digit is computed exactly the same way in both countries. Length and writing differ: an Estonian reference has 2 to 20 digits and is usually written without spaces, a Finnish one has 4 to 20 digits and is printed in groups of five from the right, without leading zeros ("12 34561"). In the Finnish bank barcode the same number is padded with zeros to 20 digits. So every Estonian reference of four or more digits that does not start with a zero is valid under the Finnish rules too.

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Can I use an Estonian reference number for a payment abroad?

Only a bank of its own country is sure to know a national reference. In another country's bank it may go through as a reference or reach the payee only as part of the message. For a payment abroad the RF reference (ISO 11649) is safer: it is the common structured reference of SEPA payments and the original number stays readable inside it. The calculator shows every reference in RF form, for example 121312952 is RF31 1213 1295 2. If the invoice gives the RF form, use it, otherwise ask the sender.

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What is the Belgian structured communication?

Belgian invoices carry a structured communication instead of a reference (in Dutch gestructureerde mededeling, in French communication structurée, OGM-VCS for short). It is 12 digits written +++010/8068/17183+++: ten digits of the sender's own choice and two check digits, the remainder of the first ten divided by 97 (a remainder of 0 is written 97). The payer types it into the field a Belgian bank's form has for it, leaving out the +++ and /.

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How do the models of a Slovenian reference (sklic) work?

A Slovenian reference starts with SI and a two-digit model, followed by up to three numbers P1, P2 and P3 joined by hyphens (20 digits at most). The model says which part ends in a check digit K: SI00 has none, SI05 is (P1)K - P2 - P3, SI12 is one 13-digit number with its check digit and SI99 means no reference. The check digit is computed modulo 11 (a result of 10 or 11 is written 0). The rules are in the Slovenian Banking Association's (ZBS) guide, version 1.4 of 2023. For taxes and other public payments the payee gives the model and the numbers, the calculator checks their structure and check digits.

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The calculator says the check digit is wrong. What now?

Most often one digit is mistyped or two neighbouring digits are swapped. The check digit catches most such mistakes. The calculator shows which check digit would be right for this base, but if the reference came from an invoice, do not fix it yourself: another digit may be the wrong one. Ask the sender, because a payment with a wrong reference does not reach the right invoice in their books.

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What is the RF form of a reference number?

The RF form is the same reference in the international ISO 11649 format: RF, two check digits and the original reference, for example the Finnish reference 12 34561 is RF34 1234 561. The check digits are computed modulo 97 as in an IBAN. The calculator shows the RF form of every Estonian, Finnish and Belgian reference, and the RF reference calculator also makes one from an invoice number with letters. On the Slovenian UPN form RF is a model of its own, made in the RF calculator.

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How do I turn a Finnish reference into a virtual barcode?

The payment part of a Finnish invoice usually has a bank barcode and its 54 digits as text, the virtual barcode (virtuaaliviivakoodi). It holds the payee's IBAN, the amount, the reference and the due date. Make the Finnish reference here and press "Make a virtual barcode", or open the virtual barcode calculator and add the FI IBAN and the amount there.

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