FAQ
Do I need an account with a service provider?
Section titled “Do I need an account with a service provider?”No. The add-on talks to the KSeF API of the Ministry of Finance directly, with your own NIP and your own KSeF token or certificate. Using KSeF is free.
Since when is KSeF mandatory?
Section titled “Since when is KSeF mandatory?”According to the Ministry of Finance (ksef.podatki.gov.pl, “Etapy wdrożenia KSeF”): from 1 February 2026 for large taxpayers, from 1 April 2026 for the other VAT payers, and from 1 January 2027 also for the smallest businesses whose invoiced sales are up to PLN 10,000 a month. Rules on penalties and their start date may change; follow the Ministry’s announcements and ask your tax advisor.
Which orders get a KSeF invoice?
Section titled “Which orders get a KSeF invoice?”Orders with a buyer tax ID (Polish NIP, EU VAT ID or another tax ID) when they reach an issue status. Consumer orders (B2C) only when you switch on B2C invoicing. You can always create an invoice by hand on the order page.
Can I test before going live?
Section titled “Can I test before going live?”Yes. Choose the Test environment of KSeF: invoices there have no legal effect and you can use test NIPs. The Demo environment works like production for a final check. Switch to Production when your invoices look right. Documents show which environment they were sent to.
Which login should I use, token or certificate?
Section titled “Which login should I use, token or certificate?”A KSeF token is the simplest: create it once in the KSeF taxpayer application and paste it in. A KSeF certificate or a qualified electronic seal works as well; the add-on signs the login with it. Both are stored encrypted.
What does the add-on check before sending?
Section titled “What does the add-on check before sending?”Every invoice is validated against the official FA(3) XSD of the Ministry of Finance (included in the add-on). The add-on also checks your NIP, the buyer NIP checksum, the seller address, the exemption basis for exempt items, unknown tax rates and whether the invoice total matches the order. KSeF itself runs further checks and the add-on shows its answer.
My store’s prices include VAT. Are the amounts right?
Section titled “My store’s prices include VAT. Are the amounts right?”Yes. With prices including VAT the add-on issues the invoice on gross values (unit prices with VAT, VAT per rate calculated from the gross total), so the invoice total equals what the customer paid.
How are EU and export sales handled?
Section titled “How are EU and export sales handled?”Untaxed sales to EU businesses with a VAT ID get 0 % intra-Community supply (or np II for services, as you set), exports outside the EU get 0 % export, OSS sales to EU consumers carry the rate of the buyer country with the WSTO_EE mark (map those taxes to OSS). Reverse charge sets the P_18 annotation.
What about split payment (MPP)?
Section titled “What about split payment (MPP)?”Mark Annex 15 products in the product editor. B2B invoices for Polish VAT payers of PLN 15,000 or more that include such products get the split payment mark. Your payment instructions remain your responsibility.
Can I change an invoice after KSeF accepted it?
Section titled “Can I change an invoice after KSeF accepted it?”No, KSeF invoices are final. Create a correction invoice instead. Invoices that KSeF rejected or that failed the checks can be rebuilt from the order with the same number.
What happens when KSeF is down?
Section titled “What happens when KSeF is down?”The invoice keeps its number and date and waits in the offline queue with its send deadline; the queue sends it in offline mode as soon as KSeF answers. Keep the cron job running.
Can I get the invoices my suppliers sent me?
Section titled “Can I get the invoices my suppliers sent me?”Yes, Incoming invoices lists them for your NIP and downloads their XML.
Is my KSeF token safe?
Section titled “Is my KSeF token safe?”It is stored encrypted with a key derived from your store’s own secret key, never shown again (only its last characters) and never written to logs. Anyone with access to your server files and database could still use it, as with any stored credential: revoke the token in the taxpayer application if you suspect a leak.
Does it work with the full page cache of CS-Cart 4.21?
Section titled “Does it work with the full page cache of CS-Cart 4.21?”Yes. Nothing is added to cached pages.
Does it slow down checkout?
Section titled “Does it slow down checkout?”No. Storefront orders only queue their invoice; sending happens in the admin panel or by cron.
What happens if the license lapses?
Section titled “What happens if the license lapses?”No new KSeF invoices or corrections are created. Invoices already created keep being sent to KSeF, and their KSeF numbers, UPO receipts and verification codes stay available.
The admin panel shows a license notice.
Section titled “The admin panel shows a license notice.”Enter your license key on the License tab of the add-on, or the CS-Cart Marketplace license number in Add-ons → Manage, and click Check now.
Does the add-on work on my staging copy?
Section titled “Does the add-on work on my staging copy?”Yes. Development hosts (localhost, .test, .local) need no license. Use the KSeF Test environment there so that no real invoices are sent from staging.
Does the license check slow down my storefront or checkout?
Section titled “Does the license check slow down my storefront or checkout?”No. The storefront only reads the stored result; checks run in the admin panel at most once a day.
Is this legal or tax advice?
Section titled “Is this legal or tax advice?”No. The add-on creates and sends invoices in the published format with the data and settings you provide. You remain responsible for the content of your invoices.
Still stuck?
Section titled “Still stuck?”Work through the troubleshooting guide, then contact support with your CS-Cart version, edition, PHP version and the add-on version (1.0.0).