IHTM28363 - Liabilities: investigating form IHT419: how to identify and handle S103 FA 1986 debts?
Taxpayers should identify any gifts made to anyone who the deceased owed money to in box 5 of form IHT419, together with details of any loans if they have not been included in box 2 of the IHT419. This should indicate that FA86/S103 may apply.
But even where box 5 is not completed you should look at who the deceased owes money to in box 2 of IHT419 and compare this with the names of the recipients of gifts on form IHT403.