Tax-Planning Calculators for Year-End (December-January)
Optimize your tax position before year-end. Tools for planning deductions, income, and tax strategies.
CalculatorZone Editorial Team10 min readPublished Updated
Year-End Tax Planning Checklist: UK Calculators for January to April
The UK tax year runs from 6 April to 5 April. The final months — January to April — are the most important for tax planning. Miss the 5 April deadline and you lose allowances that cannot be reclaimed. This checklist walks through the key actions every UK taxpayer should consider before the tax year closes.
Year-End Tax Planning Checklist
| Action | Allowance / Benefit | Deadline |
|---|---|---|
| Use ISA allowance | £20,000 tax-free per year | 5 April |
| Maximise pension contributions | £60,000 annual allowance + carry forward | 5 April |
| Crystallise CGT losses | Offset gains within £3,000 exempt | 5 April |
| Marriage allowance | Transfer £1,260 of personal allowance | 5 April |
| Gift Aid donations | Charity gets 25p per £1, HR taxpayers reclaim extra | 5 April (or carried back) |
| Junior ISA for children | £9,000 per child per year | 5 April |
| Pension carry forward | Use unused allowance from 3 prior years | 5 April |
Pension Carry Forward: A Powerful Year-End Tool
If you haven't used your full pension annual allowance in the last three tax years, you can carry forward unused allowance and make a larger contribution in the current year. The current annual allowance is £60,000. If you had unused allowance in 2023/24, 2024/25, and 2025/26, you could potentially contribute significantly more than £60,000 in a single year — a powerful tool for business owners with irregular income or anyone who has had a high earning year.
Marriage Allowance
If one partner earns below the personal allowance (£12,570) and the other is a basic rate taxpayer, the lower earner can transfer £1,260 of their personal allowance to their partner, saving up to £252 in income tax per year. You can backdate a claim to 6 April 2022 for any years you were eligible, potentially worth over £1,000 if you haven't claimed yet.