Corrective Invoice

What is supported in KSeF for corrections

What is supported in KSeF:

A "Credit Note" does not exist as a specific document type in KSeF
The supported document type is KOR, it allows:
- Scenario 1 : Corrections to compare with a credit note, where you credit some lines compared to the invoice, can be a credit of the complete invoice or a part.
- Scenario 2 : other types of corrections e.g. : price correction, change in customer and supplier data.

Sending a Corrective Invoice via Billit

Billit currently supports the above scenario 1.

How it works:

Via Billit you can create a credit note, it will automatically be converted to KOR. This can be created via the normal Billit ways:
- Via API.
- Manual creation via MyBillit user interface.
- UBL upload.
Reference to the Invoice:
- The reference to the linked invoice must be included in case of KSeF (API : AboutInvoiceNumber).
- You can only refer once to an invoice number when sending credit notes, and the total amount of the credit note should not exceed to amount of the invoice.
How to create a credit note via API : see general credit note info page : https://docs.billit.be/docs/sending-a-credit-note
The credit note will appear in the menu Income / Credit Notes.

Specific fields:

Description	Type	Billit value	KSeF Field
Type is KOR	Header	"OrderType": "CreditNote",	RodzajFaktury : KOR
Link to Invoice (Supplier Invoice Number)	Header	"AboutInvoiceNumber": "00008",	NrFaKorygowanej
Link to Invoice (KSeF Number)	Header	Lookup via Billit	NrKSeFFaKorygowanej
Type of correction	Header	Currently default : Korekta wartości. Value correction	TypKorekty : 2
Reason of the correction (description)	Header	Field is planned	PrzyczynaKorekty
Regular Line descriptions	Line	Description (supported), ExtendedDescription (planned)	FaWiersz, P_7, FaWiersz, P_7A
Line info : only the net values are applied	Line	Automatically applied by Billit	P_8B : 1

What if Invoice was issued the start of the KSeF use?

2 options below, option 2 will be supported in the near future

Description	Billit	KSeF Field
KOR refers to invoice issued with KSeF	AboutInvoiceNumber contains the reference to your previous invoice number to correct. Billit will lookup the KSeF number and included this in the KSeF field "NrKSeFFaKorygowanej"	Include ref in KSeF, NrKSeF = 1
KOR refers to invoice issued outside KSeF (before using KSeF)	AboutInvoiceNumber has no referendce	NrKSeF = 0, no need to include a reference

Not supported:

Separate Correction Note (nota korygująca, optional)

Receiving a Corrective Invoice in Billit

Below an KSeF XML example with comments (the main KOR-section of the file).

<Fa>
    <RodzajFaktury>KOR</RodzajFaktury>  //doctype is KOR
  <TypKorekty>2</TypKorekty> //Type of correction. 2 : correction with effect on the date of issue of the
corrective invoice,
    <DaneFaKorygowanej>
      <DataWystFaKorygowanej>2026-02-20</DataWystFaKorygowanej>  //Corrected Invoice Issue Date]
      <NrFaKorygowanej>00008</NrFaKorygowanej>  //Number of the correction of the previous document (example previous KOR document)
      <NrKSeF>1</NrKSeF>  //Flag of the KSeF number of the corrected (original)
invoice
      <NrKSeFFaKorygowanej>9540010231-20260220-371693400000-9B</NrKSeFFaKorygowanej>  //Corrected Invoice KSeF
Number, so this is referring to the original document, but then the KSeF number
		</DaneFaKorygowanej>  
</Fa>

Receiving a Corrective Invoice in Billit

When a corrective invoice is received from supplier, below the current way of working. This will evolve in the near future.

Receiving corrective invoice:

The corrective invoices arrives in the Fast Input. It includes the human readable.
After manual processing KOR can be viewed in menu Expenditure / Credit Notes.
Details screen contains the KSeF information (PDF not yet).
KSeF info can also be viewed on the Polish KSeF portal.