CGT tax on BTL Property

Hi, I have just received a bill for £700 as a late-fee penalty for not declaring the sale of a buy-to-let property. This was a shock as I sold the property in Nov 21 and declared on my SA tax return for 21/22 and paid the CGT. At no point in that process was anything other suggested, and my solicitors for the sale never suggested anything otherwise. I have subsequently learned that from 2020 onwards you must declare the CGT from the sale within 30/60days or pay fines. This was purely an error out of ignorance, failure of solicitors to advise and failure of understanding that rules have changed. Is there any way around this fine? Also - I jointly sold the property with my wife, will be £700 fine be doubled as the same error was made on both of our taxation? This seems unfair! Any help hugely appreciated!

Hi Tom Hitchcock,
You can send in an appeal against the penalty giving your reasons but there is no guarantee it will be accepted.
This should be sent to:
HMRC PAYE & Self Assessment BX9 1AS.
It is likely the same charges will apply to your wife.
Guidance here: 
Appeal against a penalty
Thank you.