If you operate a property in Poland and issue invoices in Mews Operations, you need to submit eligible business invoices through the national KSeF platform to meet legal requirements. You perform this action when you issue invoices for business-to-business or business-to-government transactions. This applies from February 2026 for large entities and from April 2026 for all other VAT-registered businesses in Poland. When the KSeF Fiscal Registry Integration is active, Mews automatically submits eligible invoices to KSeF for validation and legal issuance.

If you operate a property in Poland and issue invoices in Mews Operations, you need to submit eligible business invoices through the national KSeF platform to meet legal requirements. You perform this action when you issue invoices for business-to-business or business-to-government transactions. This applies from February 2026 for large entities and from April 2026 for all other VAT-registered businesses in Poland.

When the KSeF Fiscal Registry Integration is active:

1. Mews sends eligible invoices to KSeF automatically in the background.
2. KSeF converts the invoice into the required structured format.
3. KSeF validates the invoice and assigns a unique KSeF identification number

The invoice becomes legally issued only after validation.

 

In this article, you can learn about:

• How to send compliant B2B and B2G invoices to KSeF in Mews Operations
  • Prerequisites
  • Step 1: Close a bill or issue an invoice for the KSeF integration
  • Step 2: Verify invoice status after submission

 

How to send compliant B2B and B2G invoices to KSeF in Mews Operations

Prerequisites

Before you send invoices, ensure you complete the following setup:

1. The KSeF Fiscal Registry Integration is active for your property.
2. Your company details are complete, including registered name, address, and NIP.
3. You upload your KSeF certificate, private key, and password. Note: You obtain the KSeF certificate directly from the Polish Ministry of Finance. Mews does not provide this certificate.
4. Your customer profiles include a valid NIP for each business you invoice. Note: You can send invoices to entities without a NIP or Tax Identification Number, for example, a foreign embassy or consulate, by selecting the Government Entity classification in the company profile. The Tax Identifier section of the company profile should also be empty. You must share the invoice outside of KSeF as a Portable Document Format (PDF) file containing a Quick Response (QR) code.

You are responsible for complying with KSeF requirements. Mews provides integration support but does not replace your legal or tax obligations.

 

Step 1: Close a bill or issue an invoice for the KSeF integration

Follow these steps to close a bill or issue and submit an invoice for the KSeF integration:

1. In Mews Operations, open the guest or company profile.
2. Click the Billing tab, then click to select the open bill you want to process.
3. Ensure the following details are correct:
   • Check that all products, quantities, prices, taxes, and payments are correct.
   • If the bill is assigned to a company, verify the company’s:
     • Legal name
     • Tax identifier
     • Complete billing address, including country
4. Correct any missing or inaccurate information before continuing. For KSeF invoices, an invalid or missing buyer tax identifier can cause rejection.
5. You can close the bill or issue an invoice for later payment.
   • To close the bill: You close a bill when a payment is already attached.
     1. Confirm that the attached payment covers the full bill amount.
     2. Review the bill details and make sure no further payment or correction is needed.
     3. Click Close to close the bill as a paid bill.
   • To issue an invoice for later payment: You issue an invoice when the customer does not pay immediately.
     1. Click Issue invoice.
     2. Review the invoice details, including the recipient, address, tax identifier, invoice dates, due date, counter, totals, and payment information.
     3. In the Fiscal registry field, select the correct fiscal registry. For an eligible Polish invoice, KSeF should be visible in the list and selected.
     4. Confirm once more that the company tax identifier and address are correct.
     5. Click Issue and send.

 

Step 2: Verify invoice status after submission

1. In Mews Operations, go to the main menu > Finance > Fiscal record report.
2. Fill in the following details:
   • Start: Click to select the start date and time for the invoices you want to verify.
   • End: Click to select the end date and time for the invoices you want to verify.
   • Fiscal registry integration: Click to select KSeF fiscal registry integration.
   • Status: Click to select invoices according to their status.
     • Error: The invoice is invalid or KSeF responded with an error. You need to reissue the invoice as an open bill, correct the data and send the invoice again.
     • Pending: The system has sent the invoice to KSeF, has received a response and is pending validation.
     • Processing: The system has sent the invoice to KSeF and is waiting for a response.
     • Success: KSeF has validated the invoice, assigned a unique KSeF identification number and added a QR code on the invoice for verification.
3. Click View report.

If the integration is active and the invoice meets KSeF requirements, Mews automatically submits the invoice to KSeF for validation.

This sends compliant B2B and B2G invoices to KSeF in Mews Operations.