Part Private Residence Relief

I bought a flat for £310k in October 2012 which was my primary residence (50/50 with owned with wife) until 2016 when the property increased in value to around £600k. In October 2016 we remortgaged the property as a Let To Buy and bought a second property (a house) which we moved into and have been in since. The flat has been let since 201, which is 8/12 years we have owned it. The flat is still worth around £600k today. If we sold the property this year (2024), I think we would be eligible for 48 months + 9 months part private residence relief. How does these 57 months turn into a relief/reduction off of the capital gain tax bill?

Hi richardkent24,
Please refer to guidance here:
Private Residence Relief (Self Assessment helpsheet HS283)
Thank you.