Cgt on mum's main residence

Hi In 2000 due to health issues mum came to live round the corner from me. Her income Wasn't enough to cover the mortgage so my husband and myself went on the mortgage and the deeds as joint tenants. Mum has passed away and the property needs to be sold. Will myself and my husband be liable for cgt. Will there be any reduction as was mums main residence. She also had a new bathroom and porch fitted as I under stand certain things can be taken off the capital gain. The house was bought for £40k and now worth about £140k there is an interest only mortgage of £20 k which will be cleared when sold. Many thanks

Hi Lyndea31,
Your late mother will not be subject to capital gains tax on the disposal of the property, but the property will count towards inheritance tax payable by the estate.  
The mortgage is not relevant for calculating capital gain tax liability and cannot be used as a deduction.  
If the property was not named in a will, then the estate of your late mother may be liable to capital gains tax. 
If the property was named in a will and both you and your husband were the named beneficiaries, then you both may be liable to capital gains tax.  
If your mother paid for the bathroom and porch, you cannot includ them as deductions against capital gains, as you did not incur the cost.  
Please have a look at the guidance at Capital Gains Manual CG15150 - Expenditure: introduction and Expenditure: enhancement expenditure (Capital Gains Manual CG15180 - Expenditure: enhancement expenditure), as well as cost of acquisition and disposal at Capital Gains Manual CG15250 - Expenditure: incidental costs of acquisition and disposal.
Thank you.

Many thanks. What a minefield! We were all joint owners and mum said In Her will that her portion was to go to me and my husband although as joint tenants that would be the case anyway. We were all involved in the upkeep and alterations not just mum. Will have to hope for the best but expect the worst . Thanks for responding