202 Part 3 Inheritance tax It is helpful to gather information that you will need before completing the form, as none of the information can be saved to return to the form later, the application must be done in one go. Information that you will enter on screen will include: full name of the person who has died; date of death; date of birth; national insurance number. HMRC will process the online application and send the reference number by post to the personal representatives, together with the pre-referenced payslips to enable the form IHT400 to be submitted and the tax to be paid. Payment due date The due date for inheritance tax to be paid to HMRC is six months after the end of the month in which the death occurred, unless the instalment