ECL31500 - Enforcement: Penalties: Failure to notify HMRC of a repayment that should not have been made
If a person fails to notify HMRC, in writing, that an amount of levy, which could include an amount of repayment interest, has been repaid that ought not to have been repaid they will be subject to a penalty of either
(a) £250; or
(b) the amount which is 5% of the difference between the amount of levy paid as a result of the failure to make a complete and correct ECL return and the amount HMRC considers due,
This is at HMRC’s discretion.