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Resolving validation errors

Source exceptions

What to do with an item Onzli could not place in any VAT box.

Last reviewed 25 October 2026

A source exception is an item in your accounting data that Onzli cannot place in a VAT box with certainty. It appears in the validation list as an unresolved source exception and blocks the return.

Classify it

Where you are allowed to resolve exceptions, choose Record a decision next to the item.

  1. Choose what the item is from the classifications below.
  2. Write a reason in plain English. A minimum length applies.
  3. Enter your authenticator code and record the decision.

The classifications

These resolve the exception because the item is correctly outside every box:

  • Listed in Notice 700/12 as left out (money put in or taken out, loans, dividends, gifts of money, insurance claims, wages, PAYE, MOT, vehicle licence duty, rates).
  • A purchase-side payment that is not consideration for a supply.
  • A payment, clearing or balance-sheet movement: not a sale or purchase.

These are recorded, but the return stays blocked:

  • A grant, donation or compensation received (needs review).
  • Zero-rated, exempt or reduced rate: the item belongs in the return.
  • Outside UK VAT under place-of-supply rules.
  • Reverse charge: international services, gold, or the domestic reverse charge (Notice 735 categories).
  • A bookkeeping or mapping error: correct it at source.

What a classification does

  • It never changes a figure or your accounting records.
  • Only an item that is correctly outside every box resolves the exception and unblocks the return.
  • An item that belongs in the return, or is a bookkeeping error, is recorded but keeps the return blocked. Correct the source in your accounting data, then recalculate the period.
  • The decision and reason are kept in the audit trail.
  • Under dual control, the person who classified the exception cannot then approve the same return.

Next

After the item is resolved or corrected, recalculate the period. See Resolving validation errors.

Resolving validation errors

How to read the checks on a return and what to do about each kind.

Approve a return

What approval means and what you confirm when you approve.