Thank you for your reply.
My advice is that you should make a voluntary declaration to HMRC and bring your tax affairs correct. As soon as you sell the property HMRC would be aware of the sale as it has access to all transactions recorded at the Land Registry
The property is owned for say 20 years and 5 of them as main residence.
Your gain exempt from CGT is (69/240x200,000) £57,500.
Gain not covered (200,000-57,500) £142,500
say jointly owned - gains allowance (12,300x2) £24,600
Gain subject to CGT (142,500-24,600) £117,900
This would attract CGT at 18%, 28% or a combination of both depending on your total income including the gain.
Worst scenario CGT at 28% £33,112
My aim is to give you a professional service. I hope this is helpful and answers your question.
If you need more assistance, please use the reply box below and let me know. It has been my pleasure to assist you with your question.