Have I got a problem?
You need to start by adding up the total value of your assets less any liabilities (such as loans). Assets include: your home; savings and investments, chattels (antiques, cars, jewellery etc) and any other land or properties you own.
If the total figure exceeds £325,000 for an individual or £650,000 for a married couple (or civil partners) you have a potential problem because your beneficiaries will be liable to pay 40% Inheritance Tax on the excess.
There are, of course, a number of exceptions to the basic principle - for example your assets may qualify for Agricultural Property Relief or Business Property Relief meaning the relevant asset values may be removed fully or partially from the calculation. There may also be other assets that you do not consider to be part of your estate, that HMRC will include in the calculations for example: some gifts you have made within the last seven years.
If you are uncertain about any of these points (in terms of what is included and what isn't) you can rely on CLA IFP to clarify the situation.