Overview
P_7 is the name of the item or service on one line of the invoice (in Polish, "nazwa towaru lub usługi"). It lives inside each FaWiersz block and is the human-readable description that tells the buyer what they are being billed for.
Every FaWiersz needs exactly one P_7. It is a text field (TZnakowy in the XSD), so it accepts any string, but it is not free-form decoration: the Polish tax office expects a clear, accurate description of the goods or service, because the invoice line is what the buyer records in their books and what an auditor reads.
Good practice is to be specific. Instead of writing "Services", write "SaaS subscription — October" or "Technical support, 2 hours". Include enough context that the line is self-explanatory without the buyer having to ask. For recurring SaaS invoices, adding the period (a month or a date range) makes the document much easier to reconcile against a subscription.
P_7 has no numeric rules to worry about — there is no minimum length and no restricted character set beyond valid XML text. That does not mean content is unconstrained: KSeF may reject descriptions that are clearly empty or unusable, and a vague P_7 will come back to you as a support question from the buyer. Keep it short enough to read in one glance, typically under 200 characters.
In Notaly you do not send P_7 directly as a field name. You send each line item with a name property in JSON, and Notaly maps that name to P_7 in the generated FA(3) XML. If a line has no name, the API rejects the payload with a 422 validation error before anything reaches KSeF, so the mistake never costs you a sandbox invoice.
A complete, valid FA(3) example appears below, with P_7 filled on both lines.
<Faktura xmlns="http://crd.gov.pl/wzor/2025/06/25/13775/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<Naglowek>
<KodFormularza kodSystemowy="FA (3)" wersjaSchemy="1-0E">FA</KodFormularza>
<WariantFormularza>3</WariantFormularza>
<DataWytworzeniaFa>2026-10-12T07:23:07Z</DataWytworzeniaFa>
<SystemInfo>einvoice-api</SystemInfo>
</Naglowek>
<Podmiot1>
<DaneIdentyfikacyjne><NIP>2745013933</NIP><Nazwa>Example Sp. z o.o. (FICTIONAL)</Nazwa></DaneIdentyfikacyjne>
<Adres><KodKraju>PL</KodKraju><AdresL1>ul. Testowa 1, 00-001 Warszawa</AdresL1></Adres>
</Podmiot1>
<Podmiot2>
<DaneIdentyfikacyjne><NIP>1234563218</NIP><Nazwa>Test Customer S.A. (FICTIONAL)</Nazwa></DaneIdentyfikacyjne>
<Adres><KodKraju>PL</KodKraju><AdresL1>ul. Probna 2, 30-001 Kraków</AdresL1></Adres>
<JST>2</JST>
<GV>2</GV>
</Podmiot2>
<Fa>
<KodWaluty>PLN</KodWaluty>
<P_1>2026-10-12</P_1>
<P_2>FV/2026/10/001</P_2>
<P_13_1>1000.00</P_13_1><P_14_1>230.00</P_14_1>
<P_13_2>301.00</P_13_2><P_14_2>24.08</P_14_2>
<P_15>1555.08</P_15>
<Adnotacje>
<P_16>2</P_16><P_17>2</P_17><P_18>2</P_18><P_18A>2</P_18A>
<Zwolnienie><P_19N>1</P_19N></Zwolnienie>
<NoweSrodkiTransportu><P_22N>1</P_22N></NoweSrodkiTransportu>
<P_23>2</P_23>
<PMarzy><P_PMarzyN>1</P_PMarzyN></PMarzy>
</Adnotacje>
<RodzajFaktury>VAT</RodzajFaktury>
<FaWiersz>
<NrWierszaFa>1</NrWierszaFa>
<P_7>SaaS subscription - October</P_7>
<P_8A>pcs.</P_8A>
<P_8B>1</P_8B>
<P_9A>1000.00</P_9A>
<P_11>1000.00</P_11>
<P_12>23</P_12>
</FaWiersz>
<FaWiersz>
<NrWierszaFa>2</NrWierszaFa>
<P_7>Support</P_7>
<P_8A>hrs.</P_8A>
<P_8B>2</P_8B>
<P_9A>150.50</P_9A>
<P_11>301.00</P_11>
<P_12>8</P_12>
</FaWiersz>
</Fa>
</Faktura>Sources
Source: crd.gov.pl