Self Assessment Online Filing

UK Income Tax for individuals filing the SA100 Self Assessment return: who must register and file, rates and bands for England, Wales and Northern Ireland, the Personal Allowance taper, savings and dividend allowances, Finance Act 2026 rate changes, High Income Child Benefit Charge, Marriage Allowance, pension and Gift Aid relief, payments on account, deadlines, penalties and interest, with a dated section for the 2025/26 return now being filed.

UK National Insurance contributions for the 2026/27 tax year, with notes for 2025/26: employee and employer Class 1 thresholds, rates and category letters, company directors, Class 1A and 1B, the Employment Allowance, self-employed Class 2 and Class 4, voluntary Class 2 and Class 3 with their deadlines, National Insurance credits and State Pension qualifying years.

Use this skill whenever asked about UK Payments on Account (POA) for Self Assessment taxpayers. Trigger on phrases like "payments on account", "POA", "POA 2026", "January payment", "July payment", "balancing payment", "SA303", "claim to reduce", "reduce payments on account", "do I need to make payments on account", "POA threshold", "tax underpayment", "MTD ITSA payments on account", or any question about advance income tax payments under UK Self Assessment. Covers the two-payment schedule (31 January / 31 July), the GBP 1,000 threshold, the 80% PAYE test, balancing payment mechanics, SA303 claim to reduce, excluded items (Class 2 NIC, student loan, CGT), interest on late payments, the interaction with MTD ITSA quarterly updates from 6 April 2026, and interaction with tax codes. ALWAYS read this skill before touching any UK POA work.

Use this skill whenever asked about UK self-employment income for sole traders filing SA103S (short) or SA103F (full) as part of Self Assessment. Trigger on phrases like "self-employment income", "SA103", "trading income", "sole trader tax", "allowable expenses UK", "capital allowances UK", "trading allowance", "basis period", "tax year basis", "simplified expenses", "Class 4 NIC", "Class 2 abolished", "MTD ITSA", "Making Tax Digital", "April 2026 sole trader", "loss relief self-employed", or any question about computing self-employment profits for a UK sole trader. Covers trading income computation, allowable expenses, capital allowances (AIA, WDA, FYA), simplified expenses, the trading allowance, the completed basis period reform, the MTD ITSA three-phase rollout from April 2026, loss relief, and Class 4 NIC interaction (including the post-2024 rate cut and Class 2 abolition). ALWAYS read this skill before touching any UK self-employment work.