Readers’ forum: Declaring formerly joint home to HMRC

My ex and I (never married) bought a flat in London as joint tenants for £550 000. We bought the flat with a 95% mortgage. We separated in 2019 and he moved out at the end of 2019. I remained living in the flat and I bought him out in mid-2021. I only paid him approximately £8 500 to buy him out plus some furniture (essentially what he had paid towards the deposit/equity prior to us breaking up).

I lived in the flat until I moved to the US in 2023. I’m now looking to sell the flat. I don’t think I’ll get £550 000 for it as it’s a small flat in London and I think we paid too much. However I’m wondering if any CGT might be due in any event.

I don’t know if HMRC is looking at what we bought the place...