Inheritance and valuation dates

Hopefully this is a simple question. I’m the Executor for an estate that includes property and investments, including ISAs. I’m slightly confused about the dates that I use for the valuations to calculate any CGT. It seems to be straightforward for property. The valuation of a house as accepted for IHT and for Probate would be subtracted from a future price on sale. For the ISA it seems that the base valuation will be that on the date that the investment is transferred to the beneficiary; since that’s when the ISA ends. I’m slightly less sure about the other investments. Do I use the value of them as reported to HMRC/Probate on the date of death or is it the value on the date that Probate was granted (or something else)?

Hi notoriety,
The grant of probate submitted to the courts, declares the value of the assets on the death of the individual and when agreed by the courts, is the value used for Inheritance tax and Capital Gains tax purposes.
Thank you.