Invalid VAT rate in P_12: allowed values

What this error means

The VAT rate field (P_12) in one of the invoice lines has a value that isn't on the FA(3) list. The field accepts only predefined codes, such as 23, 0 KR or zw, written exactly as in the catalogue and without a percent sign.

Why it's required

In its description of P_12 in FaWiersz, the Ministry of Finance's FA(3) information brochure (broszura) gives a closed catalogue of values, and the XSD schema accepts only those. Letter case and spaces matter: 0 KR is a different value from 0KR, and zw from ZW.

Value	Meaning
`23`, `22`	standard rate
`8`, `7`	first reduced rate
`5`	second reduced rate
`4`, `3`	4% and 3% rates
`0 KR`	0% domestic, other than intra-EU supply (WDT) and export
`0 WDT`	0% on an intra-Community supply of goods (WDT)
`0 EX`	0% on an export of goods
`zw`	VAT-exempt sale
`oo`	domestic reverse charge
`np I`	supply outside Poland, not taxable in Poland (excluding Art. 100 ust. 1 pkt 4 and OSS)
`np II`	services under Art. 100 ust. 1 pkt 4 of the VAT Act

MF FA(3) information brochure, description of P_12 in FaWiersz

Our validator compares P_12 in every line against this list character by character and shows the value it found in the message. An empty or omitted P_12 doesn't trigger this error. The brochure allows the rate to be left out under the margin scheme, for exempt sales referred to in Art. 106b ust. 3 pkt 2 of the VAT Act, and on a simplified invoice.

How to fix it

Check the message for the line and value the validator flagged.
Pick a code from the table. For a 0% rate, always give the variant: 0 KR, 0 WDT or 0 EX.
Remove the % sign, any decimals, and leading or trailing spaces.

<!-- ❌ Percent sign -->
<P_12>23%</P_12>
<!-- ❌ Number with decimals -->
<P_12>23.00</P_12>
<!-- ❌ Bare 0, no variant -->
<P_12>0</P_12>
<!-- ❌ Uppercase -->
<P_12>ZW</P_12>
<!-- ❌ Missing space -->
<P_12>npI</P_12>
<!-- ✅ Valid codes -->
<P_12>23</P_12>
<P_12>0 KR</P_12>
<P_12>zw</P_12>
<P_12>np I</P_12>

oo applies only to domestic reverse charge. On an invoice for a foreign buyer who accounts for VAT in their own country, the brochure points to np I or np II. The validator checks this with a separate rule.

Where it usually comes from

The program or spreadsheet stores the rate as a number or as display text (23%, 23.00, ZW) and exports it to XML without mapping it to an FA(3) code. The other source is a 0% rate written as a bare 0, with no indication of whether it's a domestic sale, WDT or export.

How to choose the rate for customers in other countries is explained in our post on invoicing a foreign buyer. A short version of this list is in the overview of the most common FA(3) errors. Once you've fixed it, check the invoice again.