Invalid bank account number on an FA(3) invoice

What this message means

The account number on the invoice has the wrong length. A Polish account number (NRB) has 26 digits, and in IBAN format it's 28 characters: "PL" followed by the same 26 digits. Any other length almost always means a digit was dropped or added, or there are spaces between the groups of digits.

The validator checks Platnosc/RachunekBankowy/NrRB (the first one if there are several accounts) and reports an error when:

• the number starts with PL and isn't exactly 28 characters long,
• the number is all digits and isn't exactly 26 characters long.

We don't check numbers with another country prefix (such as DE), nor numbers without a prefix that contain spaces or hyphens. We also don't verify the check digits, so a number of the right length with two digits swapped will pass. Compare it against your banking app.

Why we check it

The FA(3) schema only requires NrRB to be between 10 and 34 characters (MF information brochure, or broszura, description of NrRB). This check therefore goes beyond what the Ministry of Finance requires: the schema will let through a Polish number with a missing digit. We flag it because the buyer copies the number from the invoice into their bank transfer, and the mistake only surfaces when they try to pay.

If the invoice contains a RachunekBankowy element, the NrRB field inside it is mandatory. If you don't want to give an account number, leave out RachunekBankowy entirely.

How to fix it

1. Copy the account number from your banking app rather than typing it.
2. Remove spaces and hyphens.
3. Keep either 26 digits or PL plus 26 digits, with no space after the prefix.

<!-- ❌ Spaces: with the PL prefix that's 34 characters instead of 28 -->
<NrRB>PL61 1090 1014 0000 0712 1981 2874</NrRB>
<!-- ❌ 25 digits, one missing -->
<NrRB>6110901014000007121981287</NrRB>
<!-- ✅ NRB format: 26 digits -->
<NrRB>61109010140000071219812874</NrRB>
<!-- ✅ IBAN format: PL plus 26 digits -->
<Platnosc>
  <TerminPlatnosci>
    <Termin>2026-10-22</Termin>
  </TerminPlatnosci>
  <FormaPlatnosci>6</FormaPlatnosci>
  <RachunekBankowy>
    <NrRB>PL61109010140000071219812874</NrRB>
  </RachunekBankowy>
</Platnosc>

Where it usually comes from

Usually the number was typed by hand or copied from a PDF along with its spaces. If your invoicing software generates the files, check the account number in its company settings: fixing it there fixes every invoice that follows.

Next step

Other fields where FA(3) invoices most often fail are covered in the most common FA(3) validation errors. Once you've fixed it, check the invoice again.