I live in UK and I have a full-time job. If I do some part-time job on Upwork, do I just need to declare this part of addtional income in my annual tax return self assessment? And if the money I earned are saved in Upwork account, I only withdraw it 2 years later. Do I have to report it to HMRC on the year of withdraw, or on the year that my client paid into my Upwork account?