IHTM36281 | Incorrect account, information or document: repayment of tax

From HM Revenue & Customs · Inheritance Tax Manual

Repayments of tax () are due to the estate. Penalties are due from the taxpayer personally. This means that if you need to make a repayment of tax you should not delay it or withhold it because a penalty issue remains open. But you may retain part of the repayment to set-off against any penalty that may become due if you are specifically asked to do so by the taxpayers.