RM4236 | RO instructions: Vouchers on which to repay
From HM Revenue & Customs · Repayment Claims Manual
You can repay up to the amount for which you have valid vouchers (RM4004 and 4012).
Do not repay the tax on a voucher if
the taxpayer does not have title to the income on the voucher
you think the tax has been repaid already
you sent the voucher away for confirmation and Central Policy (Tax Administration Advice Team), Stockport or another District told you not to repay.