General points with regard to a single person:
The current inheritance tax nil rate band of £325,000 remains the same, however, a new “Residence Nil Rate Band (RNRB) will be phased in gradually from 6 April 2017. The RNRB will be in addition to the standard nil rate band (£325,000).
The rate of RNRB is £100,000 in 2017/18, and rises by £25,000 per year until it reaches £175,000 in 2020/21. After 2020/21, RNRB will increase in line with the Consumer Price Index (CPI).
The RNRB will take the form of an extra amount that can be offset against the value of property (or possibly assets representing it) that has at some point been occupied as a residence. It is available when the residence is transferred, usually on the death of the owner to their direct descendants. Generally, the transfer to the direct descendant must be outright, RNRB is not available if assets pass into a discretionary trust.
Married couples/Civil partnerships:
For a married couple, or civil partnership, any nil rate band or unused RNRB may be passed to the widow/widower to be used on the second death, however, the rules are quite complicated.
Wills should be reviewed to take advantage of RNRB as far as possible and nil rate band discretionary will trusts may no longer be advantageous.