UK PAYE tool
Why Is My Pay Lower This Month?
Compare two payslips line by line. We surface what may explain the drop, ranked by impact.
What a result looks like
Sample: gross down £200, tax down £40, net down £150. Largest driver: gross pay (likely fewer hours).
What we check
- Gross pay change.
- Income tax delta.
- NI delta.
- Pension delta.
- Student loan delta.
- Other deductions.
When to use this tool
- Net pay dropped suddenly.
- You returned from sick leave.
- You had a one-off bonus last month.
- You started a new pension.
What the result bands mean
Driver: gross pay
Hours / overtime / sickness pay are most likely.
Driver: tax / NI
Worth reviewing the tax code and earnings band.
Driver: deductions
Possible new pension, court order, or benefit charge.
Common mistakes
- Comparing four-weekly with monthly pay.
- Forgetting last month included a bonus.
- Mixing up gross with taxable pay.
Worked example
Last: gross £2,500, tax £250, NI £130, pension £125. Net £1,995.
This: gross £2,500, tax £400, NI £130, pension £125. Net £1,845.
Tax rose £150 with no gross change - may indicate a tax code switch worth reviewing.
Frequently asked questions
Why was my pay lower with no obvious change?
Common causes: tax code change, sick pay vs full pay, reduced overtime, new benefit deduction, or a bonus pushing tax higher last month.
Could a tax code change cause this?
Yes. A move from 1257L to BR or to a K code can drop net pay sharply. Worth reviewing.
Is this an HMRC official tool?
No. We are independent. We compare figures only - we do not access HMRC records.
Why does it ask for both months?
PAYE is cumulative - last month is the baseline used to flag what changed.
What if my hours changed?
Enter the actual gross. The tool will show that gross is the main driver of net change.
Sources
- HMRC: PAYE operation guidance.
- The Pensions Regulator: auto-enrolment.
- SLC: student loan repayment thresholds.
Last verified: 2026-05-03.
Disclaimer: Educational guidance only. Not tax or payroll advice.