Transfer of unused basic threshold to surviving spouse

[Normie]

Hello
The position is as follows:
Husband and wife legally separated, but still married. Wife dies in 2015. Whole estate of £170k left to children. Nothing left to surviving spouse. So £155k of allowance unused.
Husband dies December 2021. Estate £500k, so significant IHT liability.
Can the unused £155k of the wife's basic threshold be used to reduce that liability?
Thanks in anticipation

[Sam101]

With an estate of £500,000 you dont even need it, The residential allowance of £175,000 plus the IHT allowance of £325.000 will cover so no tax liability.

[sederunt]

With an estate of £500,000 you dont even need it, The residential allowance of £175,000 plus the IHT allowance of £325.000 will cover so no tax liability.

How do you know that the residential allowance is available? There is no information regarding house ownership or disposal destination?

[Sam101]

How do you know that the residential allowance is available? There is no information regarding house ownership or disposal destination?

I was only considering the husbands situation and assumed, rightly or wrongly, that he had a residence in which he lived. The residential allowance and the IHT allowance is sufficient to meet the £500,000 estate.

If the husband did not own a property, then I was wrong to assume that, but the Wife's allowances are not needed.

Perhaps NORMIE can clarify?

[Normie]

Sorry, I should have made it clear.

Wife's property went direct to the children, sold for £165k in August 2016.

Husband had no property, was in a care home. Sold his property in 2012-ish. The £500k is mostly in ISA's with some cash and again is going to the children.

Thanks again