RobRJBS wrote: ...property valued at £175,000 in December 2008 ...
The property was sold in January 2011 for £500,000
So deceased’s estate in 2008 had no liability to IHT and executor’s valuation of property was not agreed (ascertained) by HMRC.
In that situation the unascertained probate value does not have to be the base cost and can be revised for calculating the capital gain on the realisation in 2011.
But on materially revising up ward the base cost on form CG34 the reasons for the probate value will have to be explained and could result in negligence penalties and IHT being assessed on person who submitted IHT account 205 in 2009 if estate administration complete.
My suggestion would to involve professional help asap who is experienced in negotiating with District Valuer – the 31 Jan SA deadline is not far away!!