Estimated values for both assets and liabilities are obvious candidates for scrutiny. But you should consider these critically taking account of
If the amount is relatively small and is consistent with what else you know about the estate then you should normally accept the estimated value without question. But there are no hard and fast rules. It is a matter for your judgement in the light of all relevant facts. For example, an estimated income tax liability of £5,000 in a large estate containing substantial income producing assets might seem more realistic than a similar deduction in an equally large estate but with little or no income yield.