UK Self-Assessment First Timer: Step-by-Step Filing Guide

First Self-Assessment and the HMRC site reads like a foreign language. You tell it your employment status, your extra income and the tax year, and you get the whole thing in order: how and when to register, what paperwork to gather, and how to file without missing a box. Built for the person doing this for the first time.

I need to complete my first UK Self-Assessment tax return and I'm not sure where to start. My situation: I am a {EMPLOYMENT_STATUS} who also earned {ADDITIONAL_INCOME_SOURCE} income of approximately £{ADDITIONAL_INCOME_AMOUNT} in the tax year {TAX_YEAR}. Walk me through the entire Self-Assessment process from registering with HMRC to submitting the return. Cover: (1) how and when to register, (2) what information and records I need to gather, (3) the sections of the SA100 form I must complete, (4) key deadlines I must not miss, and (5) how to pay any tax owed. Use plain English throughout: assume I have no prior tax knowledge.