Incorrect probate valuation

Dinbar51

My father died in 2008, leaving a market garden and house to his children in his will. He had always maintained that the property had an agricultural tie. Probate was dealt with by a solicitor who obtained a valuation of the property from a surveyor. The surveyor reported that there was a tie, quoted a reference number for the tie and valued the property in light of the tie.
I am informed that a tie usually reduces the value of property by 30%. His valuation was below the IHT level and the value without the tie would also have been below the threshold.
Probate was granted in 2008. My mother continued to live at the property until her death in 2017.
The family began enquiries to find details of the tie and we located a document bearing the reference number the surveyor quoted. The document is dated 1962 and confirms planning permission was granted but makes no mention of a tie. The local council have a copy of the same document and are unable to produce any evidence of a tie. We were advised by the estate agent that we did not have to go through the process of applying to remove the tie and after an abortive attempt to obtain outline planning permission to develop some of the land, we marketed the property earlier this year. There has been considerable interest in the property from 2 adjoining landowners who have forced the price up between themselves to over £200k more than the probate valuation.
Out understanding is that we children became beneficial owners in 2008 and that we all have a personal liability for CGT on any gain since then. I have used the CGT calculator on the government website and see that my liability would be about £2.5k less were the “correct” probate valuation to be used, so I would like to know if we can get the probation valuation revised or if we need to do that and can simply tell HMRC on error was made.
I would also be interested to know if the failure to obtain further details of the tie could be professional negligence on behalf of the solicitor executor and/or the surveyor. I was hoping the solicitor might be persuaded to sort the valuation issue out for free when they realise they have been at fault. The estate agent did speak to the surveyor and he claimed to have no memory of the the property.
Sorry for the length but I felt some detail was required.

getmore4less

A lot to read.

A couple of points

Was there a life interest?

If there was no IHT the value may never have been ascertained by HMRC then you can submit valuations for CGT there is no requirement to use the probate values if you believe they were wrong.

SeniorSam

It sounds like you may feel the original solicitors have made a mistake. If so, then a letter to them stating that can only bring forth some information that may help. Tax is the result of profit, so if the profit is high, then tax will be charged accordingly.

Finally, why do you feel that someone should do work for no charge?

Sam