{"id":371,"date":"2025-11-07T14:00:04","date_gmt":"2025-11-07T13:00:04","guid":{"rendered":"https:\/\/blog.mobile-calendar.com\/?p=371"},"modified":"2026-04-12T20:26:56","modified_gmt":"2026-04-12T18:26:56","slug":"ksef-co-to-jest-jak-dziala-i-od-kiedy-bedzie-obowiazkowy","status":"publish","type":"post","link":"https:\/\/blog.mobile-calendar.com\/en\/xef-what-it-is-how-it-works-and-when-it-will-be-compulsory\/","title":{"rendered":"KSeF - what is it, how does it work and from when will it be compulsory?"},"content":{"rendered":"<p><\/p>\n\n\n\n<h4 class=\"wp-block-heading\">What is KSeF?<\/h4>\n\n\n\n<p>KSeF, i.e. <strong>National e-Invoice System<\/strong>, is the Ministry of Finance's ICT system for issuing, receiving, sending and storing invoices in a standardised electronic format (XML). Each invoice sent to KSeF receives <strong>unique identification number<\/strong>and its sending to the system means that it has been officially issued.<\/p>\n\n\n\n<p>KSeF is a major step towards the digitalisation and automation of document workflows. Thanks to it, entrepreneurs will no longer have to send invoices by e-mail or store them themselves - all documents will be available in the system by <strong>10 years<\/strong>.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">How does the KSeF work?<\/h4>\n\n\n\n<p>Instead of a traditional PDF or paper invoice, the trader issues a document in XML format compliant with the specified FA(3) structure.<br>The accounting system (e.g. mobile-calendar) sends it to KSeF via a secure API.<br>The invoice is given a KSeF number and goes to the central database of the Ministry of Finance, where it can be retrieved by the recipient.<\/p>\n\n\n\n<p>This solution eliminates formal errors, speeds up the invoicing process, facilitates accounting settlements and avoids duplicate documents.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">From when will KSeF be compulsory?<\/h4>\n\n\n\n<p>The Ministry of Finance has announced that the KSeF will be introduced in stages - so that companies have time to prepare:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>as of 1 February 2026.<\/strong> - obligation for <strong>large companies<\/strong>, i.e. companies with gross sales in 2024 exceeding <strong>PLN 200 million<\/strong>,<\/li>\n\n\n\n<li><strong>as of 1 April 2026.<\/strong> - obligation for <strong>other taxpayers<\/strong>including small and medium-sized companies and sole proprietorships,<\/li>\n\n\n\n<li><strong>from 1 January 2027<\/strong> - obligation for <strong>the smallest digitally excluded entities<\/strong>, e.g. with a very low monthly turnover.<\/li>\n<\/ul>\n\n\n\n<p>During the transition period, there will be time for systems adaptation and integration testing, as well as a more lenient approach to any formal errors.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">What does KSeF change in practice?<\/h4>\n\n\n\n<p>Thanks to KSeF:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>all invoices go into a single, secure register,<\/li>\n\n\n\n<li>the need to manually send invoices by e-mail will disappear,<\/li>\n\n\n\n<li>counterparties have immediate access to issued documents,<\/li>\n\n\n\n<li>the tax administration automatically verifies the data and correctness of the invoices,<\/li>\n\n\n\n<li>taxpayers gain full archiving of documents in the public cloud.<\/li>\n<\/ul>\n\n\n\n<p>It also makes things easier for accounting offices and accounting departments - data can be automatically imported and processed in financial systems.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">How the invoice module in mobile-calendar works<\/h4>\n\n\n\n<p>W <a href=\"https:\/\/www.mobile-calendar.com\/en\/invoicing-system\">mobile-calendar<\/a> an expanded <strong>invoice module<\/strong>which enables the issuing and sending of sales documents directly from the system. It was designed for hotel, guesthouse and flat owners who want to issue invoices simply and quickly - without the need for external accounting software.<\/p>\n\n\n\n<p>The most important functions of the invoice module in mobile-calendar are:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>issuing sales invoices<\/strong> linked to bookings in the calendar,<\/li>\n\n\n\n<li><strong>sending an invoice by e-mail<\/strong> to a visitor or contractor directly from the system,<\/li>\n\n\n\n<li><strong>archiving of all documents<\/strong> in one place - every invoice issued is saved in your panel,<\/li>\n\n\n\n<li><strong>possibility to filter and download reports<\/strong>which facilitates cooperation with accounting.<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">mobile-calendar + KSeF - what are we planning?<\/h4>\n\n\n\n<p>We are working towards a full <strong>integration with the National e-Invoice System<\/strong>.<br>Once the obligation is implemented, the invoice module in mobile-calendar will automatically:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>sent the issued invoices to KSeF,<\/li>\n\n\n\n<li>received the invoice identification number at KSeF,<\/li>\n\n\n\n<li>informed about the status of the document (e.g. accepted, rejected, in queue),<\/li>\n\n\n\n<li>ensure full compliance with the current structure and requirements of the Ministry of Finance.<\/li>\n<\/ul>\n\n\n\n<p>As a result, mobile-calendar users will not have to change their habits or install additional tools - everything will take place directly in the system, in a module they are already familiar with.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">Summary<\/h4>\n\n\n\n<p>KSeF is the biggest change to the invoicing system in years - but it is also a huge opportunity to clean up and simplify processes.<br>With the mobile-calendar integration in the pipeline, users will be able to issue and send KSeF-compliant invoices without additional paperwork, in the same intuitive environment they use every day.<\/p>\n\n\n\n<p>The mobile-calendar team is already working on this. Once the KSeF system is in place - the <strong>we will be ready.<\/strong><\/p>\n\n\n\n<p><strong>Sources:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Ministry of Finance - ksef.podatki.gov.pl<\/li>\n\n\n\n<li>enova.co.uk - \"KSeF from when and for whom?\"<\/li>\n\n\n\n<li>ifirma.co.uk - \"KSeF 2026: key dates\"<\/li>\n\n\n\n<li>pit.co.uk - \"KSeF without penalties in first year of operation\"<\/li>\n\n\n\n<li>jpk.info.pl - \"Structured e-invoice - KSeF principles\".<\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"Czym jest KSeF? KSeF, czyli Krajowy System e-Faktur, to system teleinformatyczny Ministerstwa Finans\u00f3w, kt\u00f3ry umo\u017cliwia wystawianie, odbieranie, przesy\u0142anie&hellip;","protected":false},"author":1,"featured_media":372,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"csco_singular_sidebar":"","csco_page_header_type":"","csco_page_load_nextpost":"","footnotes":""},"categories":[9,6,8,4],"tags":[208,207,161,188],"class_list":{"0":"post-371","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-poradniki","8":"category-technologie","9":"category-trendy","10":"category-zarzadzanie-obiektem","11":"tag-faktury","12":"tag-ksef","13":"tag-pms","14":"tag-porady-dla-hotelarzy","15":"cs-entry"},"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v24.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>KSeF \u2013 co to jest, jak dzia\u0142a i od kiedy b\u0119dzie obowi\u0105zkowy? - mobile-calendar<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blog.mobile-calendar.com\/en\/xef-what-it-is-how-it-works-and-when-it-will-be-compulsory\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"KSeF \u2013 co to jest, jak dzia\u0142a i od kiedy b\u0119dzie obowi\u0105zkowy? - mobile-calendar\" \/>\n<meta property=\"og:description\" content=\"Czym jest KSeF? 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