Thanks for your reply.
The CGT position is-
There will be no CGT payable on your Mother's share of the property (as the only tax payable on death is Inheritiance tax).
There will be CGT to pay on yours and your sister's share on the basis that neither of you have been living there since you acquired your respective shares 8 years ago.
This is calculated as follows- you will need to ascertain the market value of your share at the time you acquired it 8 years ago. Any increase in the market value of your share from the date you acquired it to the date you sell is the figure used to calculate the CGT.
So, if for example this figure is £100,000, you would have CGT to pay at 18% or 28% for higher rate tax payers. You can however, deduct your annual allowance
for the current financial year (£11,000) and last year's financial year (£10,900), provided you have not already used them.
So, if you have not used either of the annual allowances, the sum of £21,900 can be deducted from the figure of £100,000. This leaves you with a CGT payment of £71,800 x your tax rate (being 18% or 28%).
I hope this sets out the legal position to you and asissts.
You should of course speak to an Accountant if you so wish, once the property has been sold.