The IHT zero is £325,000. However, the surviving spouse combines both so can receive £650,000 or £1m if it includes the home. However, my brother owned three houses, all of which are worth over £300,000, and on top of that we know he had at least another £350,000 in savings. That means, as we understand it, there is tax to pay, which means she is in trouble. Also, because she may well use the IHT zero for herself now, there won't be an allowance when she dies, which means the entire estate will be taxable at 40%. I think!
1 house worth approx 300k jointly owned - brothers share automatically passes to wife.
350k in bank, if jointly owned bank account funds pass to wife
Probate is note needed for above just a copy of death certificate needed and uses no IHT allowance.
When the surviving wife dies above will form her estate and will have 325k IHT allowance (500k if passed to direct descendants - as yours brothers 500k limit will be used as below)
So that leaves 2 houses at 300k each (if solely in brothers name)
IHT tax free 325k and add 175k residence nil rate band if house passing to direct descendants.
So 100k probably taxed on @ 40%
40k due tax on brothers estate
I think the max fine for non payment of IHT is £3200 but you may want to check that as if interest is constantly accruing needs urgently dealing with.
Edit. Sorry looks like a bigger tax bill than 40k, residence nil rate band can only be used against 1 property and not split between 2
The RNRB cannot be offset against other properties owned by the deceased; for example, buy-to-let or investment properties. However, if the deceased has two qualifying residential interests, then the personal representatives can nominate which property will utilise the RNRB. It cannot be divided across two properties.