{"id":9759,"date":"2025-09-16T08:00:00","date_gmt":"2025-09-16T06:00:00","guid":{"rendered":"https:\/\/prosteit.pl\/?p=9759"},"modified":"2025-09-08T15:43:20","modified_gmt":"2025-09-08T13:43:20","slug":"ksef-2026-preparation-it","status":"publish","type":"post","link":"https:\/\/prosteit.pl\/en\/ksef-2026-preparation-it\/","title":{"rendered":"KSeF 2026: How to prepare your company from an IT perspective before it's too late"},"content":{"rendered":"
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KSeF 2026 is no longer just for accounting. It's an IT project that will touch every stage of issuing and receiving invoices. Instead of paper and PDF, we're introducing XML-structured invoices based on the FA(3) schema, communication via the KSeF API, new certificates, and offline modes. It sounds technical, but the gist is simple: if a company's systems don't communicate with KSeF, sales and billing can come to a standstill. This text is a practical guide on how to prepare the infrastructure and processes for a safe and efficient transition.<\/p>\n

What does this mean in practice for you and your team? Verifying where invoices are generated within the company and whether the software can generate the correct invoice (3). Planning ERP integration with the National e-Invoice System API, including buffers and queues in case of interruptions. Organizing authorizations and certificates so that only the right people can sign and send documents. Defining new workflow procedures, creating visualizations for contractors, and short training sessions for sales, administration, and accounting. This can be done even in a smaller company if you start methodically and step by step.<\/p>\n

Every day, we support dozens of accounting firms and manufacturing companies with KSeF migrations, ERP integrations, and invoice management. We've gathered experience from implementations and testing to provide you with specific guidance instead of generalities. We'll show you what to watch out for, what can be done immediately, and what requires planning and short tests. If you want to navigate KSeF 2026 smoothly and without downtime, start with a few simple IT decisions.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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Timeline: Key Implementation and Tool Dates<\/span><\/h2>\n

Below is a practical roadmap for KSeF 2.0 from an IT perspective. We've compiled only those milestones that have a real impact on integration, authorizations, and team performance.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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September 1, 2025<\/h4>

disabling test and DEMO environments KSeF 1.0.<\/a> New test registrations only in KSeF 2.0.<\/p>September 1, 2025<\/span><\/div><\/div>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t

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September 30, 2025<\/h4>

start of open tests KSeF 2.0 API<\/strong> for suppliers and companies. A good time to start integration scenarios and FA(3) validations.<\/p>September 30, 2025<\/span><\/div><\/div>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t

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October 15, 2025<\/h4>

possibility of integration via API with pre-production environment (DEMO)<\/strong>Use for dry testing before go-live.<\/p>October 15, 2025<\/span><\/div><\/div>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t

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November 1, 2025<\/h4>

start MCU (Certificate and Authorization Module)<\/strong>From this day on, you can grant permissions and apply for KSeF certificates<\/strong>.<\/p>November 1, 2025<\/span><\/div><\/div>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t

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November 2025<\/h4>

KSeF 2.0 Taxpayer Application<\/strong> in a test version for entrepreneurs to get to know the functions and flows before the obligation.<\/p>November 2025<\/span><\/div><\/div>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t

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January 26-31, 2026<\/h4>

technical break<\/strong> between KSeF 1.0 and 2.0. Plan for a change window and deployment freeze.<\/p>January 26-31, 2026<\/span><\/div><\/div>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t

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February 1, 2026<\/h4>

production start KSeF 2.0<\/strong>. Valid FA(3)<\/strong> (replaces FA(2)); authentication possible KSeF certificate<\/strong>; the original invoice is XML file<\/strong> in KSeF, and PDF\/paper is only a visualization. Modes offline\/offline24<\/strong> require markings QR codes<\/strong>.<\/p>February 1, 2026<\/span><\/div><\/div>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t

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April 1, 2026<\/h4>

the second stage of the KSeF obligation for other taxpayers (except the smallest "digitally excluded").<\/p>April 1, 2026<\/span><\/div><\/div>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t

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December 31, 2026<\/h4>

end tokens<\/strong>From 2027 onwards, in practice, they will be KSeF certificates<\/strong>.<\/p>December 31, 2026<\/span><\/div><\/div>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t

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January 1, 2027<\/h4>

an obligation for the smallest "digitally excluded" taxpayers (including low value of a single invoice and monthly sales).<\/p>January 1, 2027<\/span><\/div><\/div>\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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FA(3) new structured invoice schema (XML)<\/span><\/h2>\n

FA(3)<\/strong><\/a> is the target, effective from February 1, 2026 e-invoice structure<\/a> in KSeF. FA(2) remains in circulation until January 31, 2026, and from February 1, all structured invoices, including corrections and final invoices relating to documents issued before that date, are issued in FA(3). The original invoice is the XML file sent and accepted in KSeF, not a PDF or printout. The specifications and announcements were published by the Ministry of Finance.<\/p>\n

What does FA(3) consist of?<\/span><\/h3>\n

The FA(3) main diagram includes the following sections: Header, Entity1, Entity2, Entity3, Authorized Entity, Fa, Footer, Attachment<\/strong>. Elements obligatory<\/strong> are Headline, Subject1, Subject2 and Fa. Elements optional<\/strong> is Subject3, Footer and Attachment, and optional<\/strong> is the Authorized Entity. The MF brochure describes in detail the content of each section and indicates which fields are mandatory and which are not.<\/p>\n

Key rules that influence integration<\/span><\/h3>\n
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    Format and validation<\/strong>
    A file is always     XML<\/a><\/strong>, compliant with the XSD provided by the Ministry of Finance. Validation includes both schema rules and semantic rules described in the documentation and brochures. Current XSD files and examples can be found in the official knowledge base<\/a> National e-Invoice System.<\/p>\n<\/li>\n

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    Taxpayer identification<\/strong>
    The buyer's Tax Identification Number is entered only in the field Tax Identification Number<\/strong> in the element Entity2\/IdentificationData<\/strong>Entering it in the VAT number or ID number will prevent the buyer from properly sharing the invoice in KSeF. This is a common error when migrating from FA(2).<\/p>\n<\/li>\n

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    Header and versioning<\/strong>
    The header contains fields such as: FormCode<\/strong> and FormVariant<\/strong>In FA(3) the brochure indicates the FA system code with variant 3 and the schema version attribute, and DateOfManufactureFa<\/strong> given in UTC. The production date may differ from the sale date in field P_1 and from the date of actual submission to KSeF. This is important for time compliance and auditing.<\/p>\n<\/li>\n

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    Continuity of settlements<\/strong>
    As of February 1, 2026, corrections and final invoices are issued on FA(3) even if the original invoice was previously created on FA(2). Integrations must take this relationship into account when linking documents and reporting.<\/p>\n<\/li>\n<\/ol>\n

    What actually changes FA(3) with respect to FA(2)<\/span><\/h3>\n