Inheritance tax and change in value

[JABB]

Good evening guys.
I have done all the paperwork for a relative who died in December 2021. I have only just finally got letters of administration back and have started to claim shares, Isas and property values. In the 12 months which have passed, values have changed. The house "sold" for £360,000 and was waiting on the letters grant. Now this has fallen through and new offers are in the £345,000 region.
The first Isa payment was valued at £just over £50,000. They have cashed it in today at £42,000.
If everything goes like this, I am expecting the estate to be worth about £45,000 less than was submitted to the IR for inheritance tax. ( Which was paid )
Do I go back to the IR and adjust the figures with them and claim a rebate on the tax paid?

[Catz]

A friend has just sold a late relative’s house for below the value that was expected. She had paid the IT back in 2021 and recently received a rebate. She was doing everything through a solicitor though so I can’t help on the ins and outs.