KSeF, bank transfers and bank statements.
Polish business banking most often lets you download a statement as MT940, camt.053 or CSV, plus a PDF. MT940 and camt.053 import into accounting software, CSV opens in a spreadsheet, and the PDF is for reading and archiving.
KSeF penalties will start on 1 January 2028 if the act passed by the Sejm on 6 November 2026 comes into force. Without it they start on 1 January 2027, and as at 9 November 2026 that date still stands, because the Senate has not yet approved the act and the President has not signed it.
The PLN 10,000 limit lasts only until 31 December 2026. From 1 January 2027, you issue invoices to businesses in KSeF regardless of the amount or your sales. The exception for invoices from cash registers and for receipts showing the buyer's NIP of up to PLN 450 ends at the same time, so an invoice for a cash register sale to a business also has to be issued in KSeF.
From 1 January 2027, an active VAT payer that pays a KSeF invoice by bank transfer to another active VAT payer must quote the invoice's KSeF number. If one transfer covers several invoices from the same seller, the payer quotes a collective identifier (IZ) instead.