Understand the lock created by VAT and OSS filing

Filing VAT or OSS protects the accounting period behind that filing.

Review the explanation

1. Open the VAT overview.
2. Find What happens when I mark a return as filed? in the frequently asked questions.
3. Review the filing effect before confirming a return.

Cybooks maintains one tax-lock date at the latest filed VAT or OSS period end. Filing an older return afterwards does not move that date backwards. Completing a VIES return does not advance it.

Viewing the overview does not lock a period. If a later accounting change is blocked by a filed period, use the correction process appropriate to that filing; an ordinary editing permission does not remove the tax lock.