Pay As You Earn
Who this guide is for: For employees, payroll staff and anyone trying to understand why take-home pay moves from month to month.
PAYE (Pay As You Earn) is the system employers use to deduct Income Tax and National Insurance from employees' pay during the year and send those amounts to HMRC.
Your tax code tells payroll how much Income Tax to take. National Insurance uses separate category letters and thresholds.
From gross pay to take-home
- Step 1Gross pay
- Step 2Pension (if salary sacrifice or net pay)
- Step 3Income Tax
- Step 4Employee National Insurance
- Step 5Student loans
- Step 6Net pay
Estimate take-home pay from gross salary Use the Income Tax Calculator
Who does what
- Employer: runs payroll, applies your tax code and NI category, deducts amounts and remits them to HMRC.
- Employee: receives net pay; should check the payslip code and report incorrect details.
- HMRC: issues tax codes, receives PAYE payments and reconciles your annual record.
- Tax code: sets how much tax-free pay payroll allows for Income Tax — see Tax Codes Explained.
- Payroll period: weekly, monthly or other frequencies change how thresholds and allowances are applied in each run.
- Year-end reconciliation: HMRC compares what was deducted with what your record suggests you owed. Under- or overpayments can be collected or repaid later.
Why your PAYE deduction can change from one month to the next
- Cumulative tax codes: most codes look at pay and tax to date in the tax year, so a quiet month followed by a busy one can change the deduction percentage.
- Bonuses and overtime: extra taxable pay in one period can use up remaining basic-rate room and increase Income Tax (and sometimes student loan) deductions.
- Changing jobs: a new employer may start without full year-to-date figures until your P45 or HMRC update arrives.
- Emergency codes: temporary non-cumulative treatment can over-deduct until the correct code applies — see Emergency Tax Codes Explained.
- Payroll frequency: moving between weekly and monthly pay changes how period thresholds are applied.
- Taxable benefits: company cars and other benefits can adjust your code mid-year.
Student loan deductions and pension contributions also affect net pay — see Student Loan Repayments Explained and Pension Tax Relief Explained.
Leaving or joining a job
A P45 passes your tax code and pay-to-date figures to a new employer. Without it, you may start on an emergency code until HMRC updates payroll.