Every entry below is the rule as Serbia publishes it. It is a reference, not a calendar: where a deadline runs from something only you know, this page says so instead of showing a date.
This is the rule as published by the registry, checked against the primary source on the date shown. It is not your filing date. Where a deadline runs from incorporation, from a fiscal year the company itself elects, or from an event only you know about, no date can be derived here at all — the figure you see is the formula, not the answer. Extensions, transitional regimes and entity-specific exemptions are not reflected. Confirm with the registry before you rely on a date.
The tax period for corporate income tax is the business year, and the business year is the calendar year by force of law rather than by the company's choice. Article 38 of the Law on Corporate Income Tax provides that «Порески период за који се обрачунава порез на добит је пословна година» and that «Пословна година је календарска година, осим у случају престанка или отпочињања обављања делатности у току године». A taxpayer may move away from the calendar year, but only through an approval: paragraph 3 requires the consent of the minister responsible for finance, or of the Governor of the National Bank of Serbia, after which the competent tax authority «одобрава решењем да се пословна година и календарска година разликују», with a tax period of twelve months, and «Тако одобрени порески период обвезник је дужан да примењује најмање пет година». Because the calendar year is the statute's own rule and leaving it costs an approval plus a five-year commitment, the annual duty below is counted from the end of the tax period. For the stub period that precedes an approved non-calendar year, paragraph 4 counts the deadline differently, «у року од десет дана од дана истека рока прописаног за подношење финансијских извештаја», so that transition is not the same formula as the ordinary annual one.