UK self-assessment tax becomes complex with: rental income, foreign income, side businesses, capital gains, dividends, multiple income sources. Accountant fee (£300-800/year) often pays for itself through identified optimisations and avoided errors.
When to hire one
Self-employed or freelance income. Multiple property rentals. Significant investment income. Complex life situations (separation, inheritance, business sale). Income over £100k (taper zone optimisation).
When DIY works
Single PAYE source. Modest savings interest. No complex circumstances. HMRC online filing handles this fine.
Even if you DIY most years, one professional review every few years usually identifies optimisations you've missed.