Short answer
A submitted VAT return is locked because it represents filed history and should not change silently after submission. Later eligible transactions are handled through the next open VAT period or an appropriate correction process.
What to check first
Why this happens
A filed return is evidence of what was submitted to HMRC. Allowing ordinary editing afterwards would make the ledger and report no longer agree to the filing evidence and could change a statutory return without a traceable correction.
Steps to resolve it
- Do not edit the submitted return itself.
- Correct the underlying transaction if the accounting record is wrong and the workflow permits it.
- Allow late eligible items to flow to the next open return where that is the intended treatment.
- For a material error in filed history, follow the practice’s VAT correction process and HMRC rules.
- Retain the original filing evidence and document the correction.
What to avoid
Frequently asked questions
Why does Balansix lock VAT after submission?
To preserve the relationship between the accounting record, the submitted return and the figures submitted to HMRC.
What happens to a transaction entered after the VAT return was filed?
Where the prior period is locked, eligible late items are carried into the next open return rather than silently changing the submitted return.
Can an authorised user reopen a filed VAT return?
A filed statutory return should not be treated like an ordinary draft period. Genuine corrections need a controlled process that preserves the original submission evidence.