IHTM10036 | IHT 400: Estate in the UK - jointly owned assets (page 6)
From HM Revenue & Customs · Inheritance Tax Manual
Boxes 49 and 50 on page 6 of the IHT400 give details of any property that the deceased owned jointly with someone else. If figures have been entered in either of these boxes form IHT404 -Jointly owned assets, should be filled in. You can find the details of the assets on this form. The taxpayers should have carried global figures over from the IHT404 for
the assets on which tax can be paid by instalments into box 49, column B
the assets on which tax cannot be paid by instalments into box 50, column A.
This follows the same formatting as the rest of the form with Instalment Option Property (IOP) listed in column B and Non-instalment Option Property (NIOP) listed in column A.