# Tax returns in Slovakia: deadlines, extensions and what shifts with them > Missing the deadline is one of the few mistakes that cannot be undone. Zdroj: https://mojatv.eu/en/blog/tax-return-deadlines-slovakia Publikované: 29.07.2026 ## V skratke - The return is filed within three months of the end of the tax period — by 31 March for a calendar year. - The deadline can be extended by three months, or six if you have foreign-source income. - The extension notice is not an application — the tax authority does not approve it, it just has to be filed on time. - A voluntary supplementary return is always better than the same error found by an audit. Tax return deadlines in Slovakia are fixed, and missing one is among the few mistakes that cannot be undone. The standard deadline The income tax return is filed within three calendar months of the end of the tax period. For a calendar year that means by 31 March. The tax is payable by the same date. Extension The deadline can be extended by a notice filed before the original deadline expires: by up to three full calendar months by up to six months if your income includes foreign-source income The notice is filed electronically on the prescribed form. It is not an application — the tax authority does not approve it; it simply has to be filed in time. What shifts along with the return An extension also moves the date from which the new social insurance assessment base applies — from 1 July with the standard deadline, from 1 October with an extended one. That is worth weighing before deciding. Penalties Failing to file on time carries a fine; late payment carries interest for each day of delay. The two are cumulative. Supplementary returns If you discover an error after filing, you submit a supplementary return. One rule is worth knowing: a voluntary supplementary return is always better than the same error found by an auditor. --- PRO Accounting, s.r.o. · +421 944 430 844 · info@proaccounting.sk