Self Assessment tax calculator
Payments on Account often surprise filers in their second self-assessment year. The 31 January demand combines the prior-year balancing payment with the first 50% Payment on Account toward the new year, so the cash required can reach 150% of the headline tax figure. The system catches up again at 31 July with POA2.
This tool calculates your total liability, splits it into the balancing payment and POA instalments, and explains payments on account. MTD eligibility needs the gross income from the specified earlier return year, which these profit inputs do not provide.
Your Tax Year
What this changes
Trading profit after allowable expenses and capital allowances, before personal pension contributions. Enter pension payments separately below. Profit is used for Income Tax and Class 4 National Insurance; it is not the gross-income test for MTD.
What this changes
Taxable rental profit before any residential finance-cost tax reduction. This input uses ordinary Income Tax rates. Do not include dividends or savings interest. Use the Section 24 calculator for a property with restricted mortgage-interest relief.
What this changes
Gross employment income from your P60. Income tax on this has already been collected at source and counts toward "tax already deducted", Enter the Income Tax deducted separately; entering salary does not automatically enter its tax deduction.
What this changes
Tax already paid through PAYE or other deductions at source. Subtracted from total liability to give the balancing payment due 31 January. If deducted tax covers more than 80% of your liability, payments on account are not triggered.
What this changes
Net contribution paid into a personal pension (the cash leaving your bank). Your pension provider claims basic-rate relief equal to 25% of your net payment, so the gross figure widens your basic-rate band. Higher and additional-rate taxpayers claim the extra relief here, often turning a "balancing payment" into a refund.
What this changes
Plans 1, 2, 4 and 5 repay at 9% above the plan threshold. Postgraduate loans repay at 6%. The repayment is included in the balancing payment, but not in payments on account.
Enter both payments towards this tax year. These reduce the balance, but not the calculation of next year's payments on account.
Enter deductions for the selected loan plan only. The result includes the remaining repayment for this year.
What this changes
CIS contractors deduct 20% from your labour invoices and pay it to HMRC. The deduction counts as tax already paid, so heavy CIS deductions often produce a refund rather than a balancing payment when your actual liability is lower.
Cash needed by 31 January 2028
Rates current for tax year 2026/27
These calculators are diagnostic tools intended to give you an initial estimate. They are not a substitute for personalised advice on your specific circumstances. Figures depend on the inputs you provide and on tax rules that change over time. Speak to us before acting on any result.
A CIMA Chartered Management Accountant will review your details and send you a tailored breakdown.
POA is triggered when Income Tax and Class 4 NI still due after tax deducted at source is at least £1,000, unless more than 80% was deducted at source. Student loan repayments are included in the balancing payment, not the POA figures. Assumes pension tax relief is available within your earnings and allowances. Child Benefit charges, savings, dividends, gains, Class 1/Class 4 annual maximum adjustments and more than one loan plan are excluded. Rental income enters loan assessment only above £2,000. MTD uses gross income and the relevant earlier return year. Check your MTD start date.