You see a CIS mismatch error when the invoice and credit note you're matching don't have the same CIS details. This usually happens because one is missing information or the CIS deduction rate or labour amount doesn't match.
If you ignore the warning and continue, your CIS reporting can be wrong and cause issues on your monthly return. It's important to fix the mismatch before you proceed.
What to do
Scenario one: The credit note has no CIS deductions
If a subcontractor issues a credit note for non- CIS work, but you want to use it against a CIS invoice:
- Record the CIS invoice as paid in full.
- Refund the credit note for the same amount and date as the invoice payment.
This approach clears the allocation and keeps your CIS records accurate.
Scenario two: Different deduction rates
If deduction rates differ (for example, 20% on the invoice and 30% on the credit note):
Both parties could need to make these changes.
Scenario three: Different CIS labour amounts
Don't allocate a CIS invoice and credit note if the labour amounts differ. Refund the incorrect document then reissue with the correct CIS labour amount.
