Gift of single nil rate band

Hello all,

I am drafting a Will for a married couple. W is a widow with full TNRB available from that previous death. H was not married before.

In order to take advantage of all 3 nil rate bands I intend to (on first deaths) make a gift of the nil rate sum to a DT. However, I want to ensure that she only uses up a single NRB on her first death (and not double). This is for practical reasons (she has about £325k in cash and a house). They’re a bit twitchy about putting a full £650k into the DT (although I accept that this would work from a tax perspective).

Is this the right solution? If so, I am struggling with the drafting. All the precedents describe the nil rate sum as the ‘maximum amount that can be left without IHT…’ etc…

Is it as simple as saying something like… the nil rate sum is an amount equal to the nil rate band for inheritance tax at the date of my death…or similar?

Am I missing something?

Also, the IHT402 doesn’t seem to be able to cope with this on the second death - it doesn’t appear to take into account any TNRB from a previous death…

Many thanks