Information on Issuing and Receiving Invoices via the National e-Invoicing System (KSeF)

1. Sales Invoices
In connection with the entry into force of regulations introducing the National e-Invoicing System (KSeF), Mostostal Warszawa S.A. hereby informs that as of 1 February 2026 it will issue and make available sales invoices exclusively via KSeF (subject to exceptions expressly provided for in tax regulations).

2. Purchase Invoices

a) Rules for Delivery of Invoices
If you are covered by the mandatory KSeF as of 1 February 2026, the existing rules for invoice delivery specified in contracts/orders concluded to date shall cease to apply. The moment of issuing and receiving invoices shall be determined in accordance with the definitions arising from the provisions of the VAT Act. For other entities not subject to mandatory KSeF, contractual provisions shall remain in force.

In cases where issuing invoices via KSeF is mandatory for you, invoices delivered in a manner other than via KSeF shall not be treated as a basis for payment, subject to point 4 below.

Each invoice issued via KSeF, in addition to the standard invoice elements required by law, must obligatorily include the number of the relevant contract/order or the Cost Center (MPK) number of the construction site or general cost unit of Mostostal Warszawa (in the KSeF invoice fields described as “Contract Number” or “Additional Description”).

b) Date of Issuance and Receipt of an Invoice (also applies to sales invoices issued by Mostostal Warszawa)
Taking into account the provisions of the VAT Act (inter alia for the purpose of determining payment deadlines), Mostostal Warszawa S.A. shall assume that the invoice issue date is the date indicated on the invoice, while the date of receipt of an invoice issued by you via KSeF is the date on which the KSeF number is assigned to that invoice (subject to situations where, during a transitional period, some taxpayers may be allowed to issue invoices in the previous form or in cases of system unavailability/failure – in such cases, the relevant tax regulations shall apply).

c) Attachments to Invoices
In cases where, in accordance with contracts/orders concluded with you, attachments (e.g. acceptance protocols and other documents) are required to be attached to the issued invoice, such documents should be sent to the previously agreed correspondence address specified in the contracts/orders or – in the case of documents bearing a valid qualified electronic signature – to the e-mail address (in “pdf” format) indicated in the contracts/orders, no later than on the day the invoice is submitted to KSeF. The subject line of the message should include the contract/order number and the invoice number. Failure to provide documentation constituting the basis for issuing the invoice will result in refusal to post the invoice. If an acceptance protocol or other document is submitted later than the invoice issuance in KSeF, the payment deadline shall run from the date of receipt of such protocol.

d) Unavailability or Failure of KSeF
In the event of KSeF unavailability (or system failure), an invoice bearing the appropriate QR codes should be submitted electronically (in “pdf” format) to the following e-mail address: fakturyelektroniczne@mostostal.waw.pl with the contract (or order) number indicated in the subject line. Once KSeF operation is restored, the invoice should be submitted to KSeF within the deadlines resulting from applicable legal provisions.