。
The warranty is for one year.
Literal
Warranty [topic-は] one year-duration is (polite).
A minimal business-polite sentence. 保証 is 'warranty/guarantee' (distinct from homophone 保障 'security/protection' and 補償 'compensation' — the 保 cluster is a minefield for learners). 一年間 specifies the duration; 間 is the span suffix.