Inherited property – considering selling – questions about CGT and gifted share from my mum

Hi all, hoping someone can help clarify a few things.

About four years ago, my sister and I each inherited a 25% share of a property from our aunt (so 50% total between us). The remaining 50% was already owned by our mum — she had inherited it from her dad back in 2006, when it was valued at around £60,000 - just before the financial crash

At the time of our aunt’s death in 2020, the property was valued at about £40,000 (though I suspect that may have been an underestimate and house prices were in a strange place). It’s in a NW industrial town and prices have risen over the past couple of years since the pandemic a bit. I’ve just had it revalued and it’s now worth around £120,000–£130,000.

In 2024, my mum gifted me her 50% share. So currently, I own 75% (50% from her, 25% inherited from our aunt), and my sister still owns the other 25%.

We’re now seriously considering selling the property. It hasn’t brought in much beyond a small amount of rental income, and my sister is keen to sell — especially now we’ve had a builder quote us £6k just to repoint the place.

I have a few questions:

1. Capital Gains Tax (CGT): If I sell now, how would CGT be calculated, given that part of the property was inherited and part was gifted to me, all at different times and valuations?

2. Gifted share from my mum (2024): Our solicitor suggested we could use the 2024 valuation to set the base cost of the gift, which might reduce CGT. Would this have any implications for me or my mum (either now or in the future, e.g. for IHT)? (The solicitors where not very helpful but suggested that they used the 2020 valuation on the gift)

3. Do I owe anything to my mum? She gifted me her 50% share last year — are there any financial or tax obligations to her or HMRC that I might have overlooked?

Thanks in advance for any guidance — I’m just trying to make sense of it all and avoid making any costly mistakes with a property that’s been more hassle than help!