Welsh calculation · 2026/27 included
Self Assessment Tax Calculator for 2026/27
Estimate Welsh Income Tax, tax on savings and dividends, Class 4 National Insurance and the amount remaining after tax already paid.
Enter annual figures for one tax year. The result separates each type of tax, applies the Personal Allowance taper and indicates whether payments on account may arise.
Annual tax-return estimate
Calculate your estimated Self Assessment bill
Use taxable pay, taxable pension income and taxable profits—not business turnover or gross rent collected. Leave a field at zero when it does not apply.
- Total income entered
- £50,000.00
- Adjusted net income
- £50,000.00
- Personal Allowance available
- £12,570.00
- Taxable income
- £37,430.00
Liability breakdown
Nil-rate amounts used
Payments on account are indicated because the estimated relevant amount is at least £1,000 and less than 80% of the liability was deducted at source.
Adjusted net income exceeds £100,000, so the standard allowance has been reduced.
Estimate only. The submitted return, HMRC calculation and statement determine the actual liability and payment dates.
Direct answer
What does a Self Assessment tax calculator work out?
A Self Assessment tax calculator combines taxable income from the same tax year, applies the available Personal Allowance and charges each income type at the rates that apply to it. Non-savings income is considered first, followed by savings and dividends.
Where self-employment profit is entered, this calculator adds Class 4 National Insurance. Tax deducted under PAYE or CIS and payments on account already made are then credited when estimating the balance.
It does not decide whether income is taxable, which expenses or losses can be claimed, or whether a figure belongs in a particular return box.
2026/27 calculation order
How the Welsh Self Assessment estimate is built
The order matters because savings and dividends sit on top of other taxable income and can cross into higher tax bands.
- 01
Combine taxable income
Employment, pension, self-employment, property and other non-savings income are added to savings and dividends.
- 02
Calculate adjusted net income
Gross qualifying relief-at-source pension contributions and Gift Aid are deducted for this estimate.
- 03
Allocate the Personal Allowance
The allowance is used against income in the order that produces the lower estimated liability and is tapered above £100,000.
- 04
Apply tax bands and nil rates
Main, savings and dividend rates are applied in sequence, including the savings and dividend nil-rate amounts.
- 05
Add Class 4 National Insurance
Class 4 is calculated solely from the self-employment profit entered and the selected year’s limits.
- 06
Credit tax and payments made
Tax deducted and earlier payments on account reduce the estimated balancing amount.
Current figures
Self Assessment rates used for 2026/27
The Welsh main rates apply to non-savings, non-dividend income. Savings and dividends have separate rules.
Non-savings income
- Basic
- 20%
- Higher
- 40%
- Additional
- 45%
Above £500 allowance
- Basic band
- 10.75%
- Higher band
- 35.75%
- Additional band
- 39.35%
Self-employed profits
- £12,570–£50,270
- 6%
- Above £50,270
- 2%
- Below £12,570
- 0%
The starting rate for savings is up to £5,000 and reduces as other income exceeds the Personal Allowance. The Personal Savings Allowance is normally £1,000 for a basic-rate taxpayer, £500 for a higher-rate taxpayer and £0 for an additional-rate taxpayer.
Official sources: Income Tax and dividend rates, savings allowances and National Insurance rates.
January may include more than the balance
How payments on account affect a Self Assessment bill
Payments on account are advance instalments towards the following year. Each is normally half of the relevant amount for the current year and Class 4 National Insurance is included.
This tool gives an indication only. HMRC’s statement controls the amount due. Read the official payments on account guidance or use the dedicated payments-on-account calculator.
Scope before certainty
What this calculator does not include
Some return entries require facts and records that cannot be established from a single amount.
Disposal proceeds, costs, losses, annual exemption and asset-specific rates require a separate calculation.
Capital Gains Tax Calculator →Student loans, High Income Child Benefit Charge, pension annual allowance charges and Marriage Allowance are excluded.
Trading losses, property losses, finance-cost relief, foreign tax credit and specialist reliefs are not calculated.
Voluntary Class 2, deferment, multiple trades and annual maximum restrictions are outside the estimate.
Use records from one tax year
Figures to gather before calculating your tax return
P60, P45 and P11D
Taxable pay, benefits and PAYE deducted.
Accounts and expense records
Taxable profit rather than bank receipts or invoices raised.
Rental statement
Your taxable share after allowable expenses and losses.
Interest and dividend records
Gross interest and dividends outside tax-exempt accounts.
Pension and Gift Aid evidence
The correct gross qualifying amounts for the year.
HMRC statement and CIS records
Tax deducted and payments on account already credited.
Common questions
Questions about the 2026/27 Self Assessment estimate
Does this calculator include the new 2026/27 dividend rates?
Yes. For dividends above the £500 allowance, it uses 10.75% in the basic band, 35.75% in the higher band and 39.35% in the additional band.
Does it calculate National Insurance for self-employed people?
It calculates Class 4 National Insurance from the self-employment profit entered. It does not calculate voluntary Class 2 contributions, deferment or restrictions involving several employments or trades.
Why are savings and dividends calculated after other income?
UK tax rules stack non-savings income first, then savings and then dividends. This determines which tax bands apply to the later income sources.
Are payments on account part of the tax liability?
No. They are advance payments towards the following year. The result separates the current balancing amount from the indicative first and second payments on account.
Can I enter rental income received?
Enter taxable property profit, not gross rent. Allowable expenses, ownership shares, losses and residential finance-cost rules should be worked out first.
Can this result be used as an SA302?
No. An SA302 is produced from a submitted Self Assessment calculation. This result is an estimate for checking and planning before filing.
Confidential enquiry
Need the return calculation checked?
Tell us which income sources are involved, the tax year and the point that needs attention. Do not send your UTR, National Insurance number or bank details through this form.
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