Does a flat-rate entrepreneur have to file an annual financial report with APR?

As a rule, no — not in the same form as a DOO (limited liability company). A typical paušalni preduzetnik (flat-rate entrepreneur) keeps the KPO knjiga (revenue ledger) and pays obligations under the assessment decision of the Poreska uprava (Tax Administration). The APR annual financial statements (balance sheet / income statement) apply to entities that have that obligation under the Accounting Act — check whether that applies to you (e.g. if you have employees or exceed the prescribed thresholds).

What a flat-rate entrepreneur tracks during the year

The Tax Administration's assessment decision — monthly payments of tax and contributions (by the 15th for the previous month)
KPO — the revenue ledger
The 6.000.000 RSD threshold — loss of flat-rate status if exceeded in a calendar year
The 8.000.000 RSD VAT threshold — in any 365-day period

When does the flat-rate income / assessment decision change?

The Tax Administration may amend the flat-rate tax assessment decision if:

You changed your business activity or registered office
There has been a significant change in circumstances affecting the base
You filed a request for an amendment within the prescribed deadline

APR — when a reporting obligation exists

If you have an APR reporting obligation (rare for a "pure" flat-rate entrepreneur with no employees below the thresholds):

Balance sheet and income statement
Deadline: typically 30 June for the previous year

The flat-rate taxation rulebook

The Tax Administration / Government updates the parameters (average salaries, coefficients). Follow the announcements on the website of the Serbian Tax Administration.

Deadlines at a glance

Item	Deadline	Note
Payment under the assessment decision	15th of the month	For the previous month
KPO	Throughout the year	Chronological, up to date
APR annual financial statements	30 June	Only if the obligation exists