Where a specific legacy incurs costs during administration which the estate initially pays out, but requires reimbursement from the legatee, do the following:
1. Record the expenses in PP as usual
2. When the legatee repays those expenses, you would record it as a negative admin expense. (i.e. put a minus sign in front of the repaid value)
3. Show where the repayment money was received (e.g. your client account).
See also this article for liabilities at death which need to be shown on the liabilities report for IHT form filling. e.g. a mortgage on a property which is then passed by to a legatee.