RM4124 | RO instructions: Informal vouchers
From HM Revenue & Customs · Repayment Claims Manual
An informal voucher is a statement in writing about an item of income. If the claimant does not have a formal voucher you may accept an informal statement made by the person paying the income if it
shows the name of the recipient
states that the tax has been paid
shows the nature of the payment
shows the gross amount paid
shows the period covered by the payment
shows the amount of tax deducted.
If any of this information is missing you should
return the voucher to the claimant
and
say that you cannot accept it until it is fully completed by the payer.