Inheritance Tax is the tax that is due on your estate on your death if the value of your net estate (your estate after deduction of liabilities such as your debts, funeral costs and so on) exceeds the Inheritance Tax threshold. If your net estate exceeds the Inheritance Tax threshold, that part of your net estate over the threshold will be liable to Inheritance Tax at a rate of 40%*.
Any gifts that you leave to charity in your Will are exempt from Inheritance Tax and accordingly, they can reduce the amount of Inheritance Tax due on your estate. In addition, if you leave 10% or more of your net estate to a charity like Samaritans, you can opt to pay a reduced rate of Inheritance Tax of 36% on any additional part of your estate that is subject to tax*.
Inheritance Tax can be complex, but your solicitor should be able to advise you about your own position.
* The Inheritance Tax threshold is currently £325,000 (as at September 2018). The Inheritance Tax thresholds, rates and concessions described above were all correct at the time of publication, but you should speak to your solicitor or other adviser to confirm the position at the time your Will is drafted.