Financial statement can be a balance sheet (rozvaha) or/and profit and loss account (výkaz zisku a ztráty or/and cash flow statement (výkaz cash flow) or even financial statement = a court paper requiring a party to specify her/his monthly income and expenses or some other type of financial statement.

Although financial statement is probably correct in this context as well, I tend to use
annual financial report (meaning year-end account) or monthly financial report (meaning month-end account). It just sounds more definite or unambiguous to me.

I think I have also seen "final account" and "year-end account"

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Note added at 6 days (2006-04-13 14:31:58 GMT) Post-grading
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Answer to the asker's question: It doesn't need to be "annual" only but 99 % of these reports (účetní závěrka) are annual. ("Účetní závěrkou se obecně rozumí souhrn prací, který na konci každého roku završuje celoroční proces vedení účetnictví"). The other types are "extraordinary" and "interim" financial report but these are produced only in non-standard situations (e.g. change of company legal status). If I spoke about a standard ordinary "účetní závěrka" of a specific company I would not hesitate to use the word "annual" although it is not so explicitely expressed in Czech. If I had no context whatsoever I might leave out the word "annual". But again, if I say just "financial report" I lose a part of what "účetní závěrka" means in 99 % of cases. It's up to you - just look at the context.