Poland is already well into one of the most important stages of tax digitalisation. By September 2026, some of the long-discussed changes have moved from preparation to daily practice, while others are still being implemented, tested or refined. For businesses operating in Poland, the key message is clear: 2026 is no longer only about getting ready. It is now about making sure that new tax processes work reliably in day-to-day operations.
The most visible changes concern mandatory e-invoicing through the National e-Invoice System (KSeF), the new JPK_CIT reporting obligations, updated VAT reporting structures, and continuing attention to payroll and personal income tax settlements. Some obligations are already live, some have entered their first reporting cycle, and some practical consequences will continue to unfold into 2027. Below we summarise what businesses should focus on at the current stage.
1. KSeF has already become part of daily invoicing
The National e-Invoice System, commonly known as KSeF, has already been launched as the standard channel for issuing, receiving and storing structured invoices in Poland. The obligation was introduced in stages: from 1 February 2026 for taxpayers whose 2024 sales value exceeded PLN 200 million gross, and from 1 April 2026 for most other taxpayers. Small taxpayers whose monthly sales documented by invoices do not exceed PLN 10,000 gross may still benefit from a temporary postponement until 1 January 2027.
As of September 2026, many businesses are already issuing and receiving invoices through KSeF. The main challenge has therefore shifted from formal implementation to operational stability: correct authorisations, reliable invoice workflows, timely downloading of purchase invoices, correct handling of corrections and consistent communication between business teams, accounting and IT.
What KSeF changes in practice
KSeF is not only a technical invoice format. In practice, it changes the entire invoice lifecycle: issuing sales invoices, receiving purchase invoices, assigning access rights, archiving, invoice corrections, approval workflows, VAT reporting and data exchange with accounting providers. In the second half of 2026, companies should focus on whether these processes work consistently in real business scenarios. Companies should verify whether invoices are issued, received, downloaded and booked correctly through KSeF.
- Access rights and authorisations should be monitored on an ongoing basis, especially where external accounting providers issue or receive invoices on behalf of the taxpayer.
- Sales and procurement teams should use the KSeF number as part of their standard invoice-handling process.
- Contingency procedures should be tested and updated for system unavailability, offline modes and internal approval delays.
2. JPK_CIT is no longer a future project
Another major change is the introduction of electronic reporting of accounting books for CIT purposes. The new JPK_CIT obligation requires CIT taxpayers to submit accounting data in structured electronic form, including the JPK_KR_PD structure for accounting books and income tax data and the JPK_ST_KR structure for fixed assets and intangible assets.
By September 2026, the largest CIT taxpayers and tax capital groups have already entered the first practical reporting phase for financial years beginning after 31 December 2024. Other CIT taxpayers covered by monthly JPK_VAT reporting are already collecting 2026 data under the new requirements, with the first reporting linked to the annual CIT settlement for 2026. This means that JPK_CIT preparation should now be treated as an active compliance process, not a year-end exercise.
Why JPK_CIT requires early preparation
JPK_CIT significantly increases the level of detail available to the tax authorities. The files may include data on accounting entries, contractors, KSeF invoice numbers, account mapping, fixed assets and differences between accounting and tax results. In practice, the quality of 2026 bookkeeping data is already important, because errors identified only at year-end may be difficult and time-consuming to correct.
- Chart of accounts mapping should already be in place and tested against the reporting requirements.
- Accounting policies and posting instructions should be updated where current practice does not support correct JPK_CIT reporting.
- ERP and accounting systems should be checked through test exports and error reviews, not only through theoretical readiness assessments.
- Companies should continuously verify contractor data, tax tags, treatment of non-tax-deductible costs and records of fixed assets and intangible assets.
3. VAT reporting and invoice data become more connected
VAT reporting is now increasingly connected with KSeF invoice data. JPK_VAT structures include fields and indicators linked to KSeF, including invoice numbers assigned by the system and specific markings for invoices issued outside KSeF in permitted situations, such as outage or transitional cases.
For businesses, this means that VAT compliance increasingly depends on the quality of invoice flows and the consistency between KSeF, accounting records and VAT declarations. In the current stage of implementation, the most important work is reconciliation: identifying missing invoices, correcting incorrect references, checking offline or transitional cases and ensuring that VAT reporting follows the actual invoice data available in KSeF.
4. CIT areas requiring attention in 2026
In addition to JPK_CIT, companies should continue to monitor selected corporate income tax areas that are relevant for businesses operating in Poland. These include related-party financing, tax-deductibility of costs, transfer pricing documentation, withholding tax, fixed asset depreciation and the correct classification of services, licence fees and intangible assets.
The increased availability of structured accounting data means that inconsistencies between accounting treatment, tax adjustments and supporting documentation may become more visible. In September 2026, companies should not wait until year-end closing, but should already review how transactions are posted during the year and whether tax-sensitive items are documented consistently.
5. PIT and payroll: ongoing attention to employee settlements
Although the most visible 2026 changes for businesses relate to digital tax reporting, payroll and PIT settlements remain an important compliance area throughout the year. Employers should verify whether payroll system settings, employee tax declarations, reliefs and exemptions, health insurance contribution rules and employee data used for tax and social security purposes have been applied correctly in monthly payroll cycles.
For internationally active employers, additional attention should be given to cross-border work arrangements, secondments, remote work from Poland or abroad, and the correct allocation of tax and social security obligations.
6. What companies should do now
At this stage, preparation should be replaced by active monitoring and process improvement. Companies should review what has already been implemented, what still creates operational issues and what must be completed before the first annual JPK_CIT reporting and the remaining 2027 obligations.
- Check whether day-to-day KSeF invoice issuing and receiving processes work reliably.
- Review access rights and responsibilities between the company, employees and external accounting provider.
- Test JPK_CIT data exports and correct mapping or master-data issues before year-end.
- Reconcile contractor master data, including tax identification numbers and country codes.
- Review fixed asset and intangible asset registers for completeness and consistency.
- Reconcile VAT reporting with KSeF invoice numbers and invoice status.
- Update internal procedures for corrections, approvals, offline invoicing and document archiving based on actual 2026 experience.
How Leinonen can support your business
Leinonen Poland supports companies in stabilising and improving accounting, payroll and tax compliance processes under the new Polish requirements. In the current phase of 2026, we can help review how KSeF works in daily practice, test and improve JPK_CIT readiness, identify data-quality risks, coordinate with ERP providers and support ongoing compliance after implementation.
Reviewing processes can help reduce year-end pressure, improve monthly reporting quality and avoid unnecessary risks during tax reporting, closing and future audits.
