The Inheritance Tax residence nil rate band (RNRB) is a transferable allowance for married couples and civil partners (per person) when their main residence is passed down to a direct descendent such as children or grandchildren after their death. 

The allowance increased to the present maximum level of £175,000 from 6 April 2020. The allowance is available to the deceased person’s children or grandchildren. Any unused portion of the RNRB can be transferred to a surviving spouse or partner. The RNRB is on top of the existing £325,000 Inheritance Tax nil-rate band.

The allowance is available to the deceased person's children or grandchildren. Taken together with the current Inheritance Tax limit of £325,000 this means that married couples and civil partners can pass on property worth up to £1 million free of Inheritance Tax to their direct descendants. 

There is a tapering of the RNRB for estates worth more than £2 million even where the family home is left to direct descendants. The additional threshold will be reduced by £1 for every £2 that the estate is worth more than the £2 million taper threshold. This can result in the full amount of the RNRB being tapered away. 

The RNRB maximum rate of £175,000 and the taper threshold are currently frozen until at least April 2026.