Input Guidance – What to Include

• Gross Salary – Total annual salary before tax, including bonuses or commission.
• Salary Sacrifice – An agreement with your employer to REDUCE your gross salary and pay the "sacrificed" amount directly into, for example, your pension.
• Net Pay Arrangement – Your employee pension contribution is taken from your gross salary (before tax) but after National Insurance has been calculated.
• Benefit in Kind – Taxable value of company benefits like a car or private health insurance.
• Pension Received – Taxable income from state or private pensions.
• Net Rental Income – Rental income after allowable expenses.
• Other Income – Any other taxable income (e.g., freelance, trust income).
• Savings Interest – Interest from bank savings accounts before tax.
• Dividends – Dividends from shares or investments (gross).

Inputs That Affect Tax Bands

• RaS Pension Contributions – Include contributions to private pensions or SIPP from after tax income (relief at source). Limits include the lower of £60,000 or "relevant UK earnings" e.g. gross salary.
• Charitable Donations – Include Gift Aid donations made during the year from after tax income.

What’s included in the Calculation

Allowances:

• ✓Starting Rate for Savings
• ✓Savings Allowance
• ✓Dividend Allowance
• ✓Blind Person's Allowance
• ✓Marriage Allowance

Limit checks:

• ✓Personal Allowance Taper
• ✓Pension Contribution Annual Limit
• ✓Tapered Pension Annual Allowance

Warnings:

• ✓Marriage Allowance does not meet min requirements

Expansion of the Basic Rate Tax Band:

• ✓Impact of Private Pension Contributions
• ✓Impact of Charitable Donations

Known Limitations

• !Personal Allowance reordering is applied automatically, but only as “all-or-nothing” between savings and dividends — not an optimised mix to minimise total tax.
• !Student Loan Repayments are not calculated. Although often shown alongside tax in HMRC summaries, they are separate from income tax.
• !Child Benefit High Income Charge is not included. If your income exceeds £60,000 and you or your partner claim Child Benefit, a charge may apply.
• !Only current year income tax is calculated — no adjustment for refunds, payments on account, or carryovers from prior years.
• !Capital Gains Tax and National Insurance are excluded — this calculator focuses on income tax only.

Coming Soon:

• !Scottish tax is not currently included.
• !Employer pension contributions are currently not captured — which may affect tapered pension allowance accuracy above £260,000 income.

Latest Blog Post:

• UK Self Assessment Calculator: Estimate Your Tax Bill in 2025

Please Note

We think it's important that you understand the strengths and limitations of this site.

At taxgrid.co.uk we make every effort to keep up to date with the latest tax rules, but we cannot guarantee to be perfect, so please note that you use this information at your own risk as we cannot accept liability if things go wrong.

This information does not constitute financial advice.

Always do your own research to ensure it's right for your specific circumstances.