Full-time vs part-time

Full-time vs part-time employee cost UK (2025/26)

Comparing full-time and part-time employment costs is more nuanced than it looks. At the same hourly rate (£15/hour in this example), a full-time employee (37.5 hrs/week, £29,250/year) costs more in total — but employer NI as a percentage of salary is actually lower for full-time workers, because the £5,000 NI threshold is not pro-rated for hours. Two part-time workers at 20 hours per week do NOT share one threshold — each gets their own £5,000. This means splitting a full-time role into two part-time roles does not reduce the overall NI bill — it typically increases it.

UK scope: England, Scotland, Wales and Northern Ireland employer payroll planning for the 2025/26 tax year.

Sample total cost

£33,578

£2,798 per month on £29,250 salary

Employer NI

£3,638

15% above £5,000 secondary threshold (2025/26)

Pension + overheads

£690

Baseline employer pension plus configured overheads

Key assumptions — UK 2025/26

Employer NI: 15% on earnings above the £5,000 secondary threshold

Employer pension: minimum 3% on qualifying earnings £6,240–£50,270

Employment Allowance: up to £10,500 off the NI bill for eligible employers

Worked examples: £30k salary → £34,464/yr · £35k → £40,363/yr · £50k → £58,063/yr

What this page helps you check

Full-time (37.5 hrs/wk, £15/hr): salary £29,250, employer NI £3,637, pension £690, total £33,577.
Part-time 20 hrs/wk (£15/hr): salary £15,600, employer NI £1,590, pension £280, total £17,470.
Part-time 25 hrs/wk (£15/hr): salary £19,500, employer NI £2,175, pension £397, total £22,072.
The £5,000 NI threshold is NOT pro-rated for hours — it applies in full per individual employee.
NI as a share of salary: 10.2% for 20-hour worker vs 12.4% for full-time at same hourly rate.
Two 20-hr workers generate more combined NI than one 40-hr worker at the same hourly rate.

Use the live tools

Calculate employer cost for any salary Part-time employee cost guide Cost of employing by salary Employer NI by salary Auto-enrolment pension calculator

UK assumptions used

Employer NI

15% above £5,000 secondary threshold for 2025/26.

Auto-enrolment pension

Minimum employer contribution 3% on qualifying earnings.

Employment Allowance

Up to £10,500 relief in 2025/26 for eligible employers.

Official UK references

HMRC rates and thresholds Employment Allowance Pensions Regulator guidance Our methodology Our source list

Frequently asked questions

Is it cheaper to employ two part-time workers instead of one full-time?

Not on NI. Two part-time workers each get their own £5,000 threshold, and combined they generate more NI than one full-time worker at the same total hours. At £15/hour, two 20-hour workers generate combined NI of approximately £3,180/year versus £3,637 for one full-time worker. You may save on pension if part-timers earn under the £10,000 auto-enrolment trigger, and on pro-rata holiday and benefits.

Is the employer NI threshold the same for part-time and full-time workers?

Yes. The £5,000 secondary threshold is fixed per employee per tax year and is not adjusted for contracted hours. This means lower-paid part-time workers have a higher NI burden as a share of salary than full-time staff at the same hourly rate.

Do you pay pension on part-time staff?

Auto-enrolment is triggered for workers aged 22–66 earning more than £10,000/year. Part-time workers earning below £10,000 are not auto-enrolled but can opt in — in which case the employer must contribute at 3% of qualifying earnings. Workers earning between £6,240 and £10,000 are entitled to opt in.

UK coverage only. Last reviewed: 04 April 2026. Estimates use 2025/26 assumptions and are for planning, not legal or tax advice.