HMRC is encouraging tax agents to correspond with it by email where possible and has introduced a number of temporary concessions to avoid processing paper forms.
VAT errors in excess of £10,000 normally have to be reported on form VAT652, but during the coronavirus shutdown the VAT post room is closed so you need to submit this form by email to: inbox.btcnevaterrorcorrection@hmrc.gov.uk
The IHT400 and IHT100 forms normally require a “wet” signature of the trustees or personal representatives, but where there is a professional agent acting for the estate HMRC will accept a printed signature accompanied by a statement from the agent confirming that all PRs or trustees have seen and agreed the account. All payments for IHT due should be made electronically or by phone as HMRC is not accepting payments by cheque.
All work on tax enquiries has been paused so HMRC will not press you for replies to queries or ask for new information or documents until the coronavirus lock down is lifted.
The First Tier Tax Tribunals have not been sitting since 24 March, and are due to resume again on 21 April, but that shutdown period is likely to be extended. If you want to appeal to the tax tribunal against a HMRC decision you should do so within the normal 30 days, but use the online appeals service, or email.