Sale of property - IHT/CGT

ieatworms

I am Executor and beneficiary for my late father’s estate.  He  died in 2020 and probate was applied for, and a small amount of IHT paid at the time as this was over the threshold of £325,000.

 

The  house was held as tenants in common with his wife (2nd marriage).  Dad  left his half share of the property to myself and my sister.  The Will gave his wife  a life interest to stay in the property until it was sold or she died.  The life interest trust ends when she leaves the property.

 

She has now gone into a care home and the property needs to be sold.  The property at the time of probate was valued at £900,000 and is now for sale for £1.5 million.  The proceeds of the sale will be split between the beneficiaries of my late father’s estate and my stepmother.

 

My question is how do we deal with any IHT/CGT due on my late father’s estate?  His RNIB was not used at the time probate was granted because of the life interest trust. 

 

Do we calculate the IHT as the difference between £1.5 million and £900,000, so our half share would be I presume, half of £1.5 million = £750,000 and half of the valuation at the time of death, £450,000, making the total 'gain' as it were of £300,000, or do we pay CGT on this amount, or something else? I presume we can apply the unused RNIB for IHT pruposes?