What you need to know about the Real Time Capital Gains Tax Service
Starting from April 2020, all UK tax residents who sell property for a profit (except, of course, your home) have to use only the Real Time Capital Gains Tax Service.
If you use the real time service:
you’ll get a payment reference number instead of a UTR
you won’t have to file a Self Assessment tax return every year – unless your income changes significantly during the year (there are different CGT rates if your income is under or over £50,270), or if you have another reason to file a tax return (for example, you earned rental income)