Poland implements mandatory KSeF e-invoicing system

Poland is implementing a mandatory B2B e-invoicing system known as KSeF. Under the new regulations, the largest companies must use the system starting February 1, 2026, while all other businesses must comply by April 1, 2026. Notably, the requirement to receive invoices through the KSeF API begins for everyone on February 1, 2026, whereas the April deadline specifically applies to the issuance of invoices.

While automatic penalties for errors made within the KSeF system are deferred until 2028, experts warn that this does not grant total freedom. There is a distinction between making technical errors within the system and completely ignoring the legal obligation to use it. Businesses that fail to use the system may still be required to provide explanations to tax authorities. Small sellers with monthly gross sales of 10,000 PLN or less are exempt from the issuance requirement until the end of 2026.

For digital businesses, integration challenges include managing tax ID (NIP) collection at checkout and handling API rate limits. Experts recommend batching invoice transmissions rather than calling the API for every individual order to avoid technical disruptions.