nominating principle residence

My wife and I have each owned and lived in our own residential properties for more than 20 years. We married in June 2016 but continued to live apart. My wife sold her home and bought and started to live in a new home in March 2023. We wish to nominate my home as our main residence for purposes of Capital Gains Tax. I wrote to Capital Gains Tax Queries BX9 1AS in July to inform HMRC of our decision but have received no acknowledgement. To whom should we write to inform of our decision and what information should we include?

Hi,
It is likely that your letter is still in the queue to be dealt with. You can contact our Income Tax team to progress chase your letter.
Income Tax: general enquiries
If we did not recieve it, you can write us and mention that you have written previously to record details of your main residence:
H.M. Revenue and Customs,
Pay As You Earn and Self Assessment,
BX9 1AS
Thank you.