Inheritance tax: Investigations into underpaid bills have reaped £1.36bn in recent yearsYou need to be worth at least £325,000 if you are single, or £650,000 jointly if you are married, before becoming liable for death duties. This is Money's guide to inheritance tax explains more. 'This "reservation of benefit" can mean that the item is included in their inheritance tax calculation.' Heather Rogers, This is Money's tax expert and the founder of Aston Accountancy, warns in our guide to paying inheritance tax to take care with property valuations. If inheritance tax is paid late then interest will also be due, plus further penalties for the delay, for example if you have no reasonable excuse.