Confirm My Residential Capital Gains Tax Calculation ?

I’m trying to help a friend calculate their potential capital gains liability if they sell their home., Based on what I was advised via this sub in the past, and from reading online, my understanding is as follows, let’s say ……

Bought House for £100k Sold House for £375k Costs to buy/sell house of £10k Capital Gain = £265k

You then need to take key dates of the above and divide that gain by the number of years in scope. So if the property was bought in 2000 and sold in 2025, that’s 25 years. So, if your gain was £265k you would divide that by 25 years, to give you your gain per year.. (£10,600)

You then factor in some deductions (1) any time it was your primary residence and (2) a 9 month allowance that HMRC give to buy/sell etc. Which would make it..

Ownership overall = 25 years Primary residence = 6 years Allowance = 9 months Applicable Years = 18.25

With all those in place you would then take the Gain per year (£10,600) times that by the applicable years (18.25) to give you your chargeable capital gain.

£10.6k x 18.25 = £193,450

From there you take off your annual capital gains tax allowance (£3k) and then divide what’s left by the capital gains tax rate of 28% - giving you a tax bill of £53.326..

Is the above in the right ball park (anything missed ?)

I’ve told them they should meet with a financial advisor/accountant for a more accurate picture - or use the Gov.uk site