I would really appreciate some help to ascertain whether my partner and I are being charged the correct income tax and national insurance contribution deductions.

I started employment on 1/5/17 (1 month after tax year start), and my partner 3/7/17 (3 months after tax year start).

Below are the deductions from our respective wage slips.

Me: annual salary £35000, tax code 1150L.

  • May: Gross pay: £2917 - Income tax: £200.20 - NI: £268.36 - Net pay £2448.44
  • June: Gross pay: £2917 - Income tax: £391.80 - NI: £268.36 - Net pay £2256.84
  • July: Gross pay: £2917 - Income tax: £391.80 - NI: £268.36 - Net pay £2256.84
  • August: Gross pay: £2917 - Income tax: £391.80 - NI: £268.36 - Net pay £2256.84

Partner: annual salary £29500, tax code 1150L.

  • July: Gross pay: £2458 - Income tax: £0 - NI: £213.60 - Net pay £2244.40
  • August: Gross pay: £2458 - Income tax: £24 - NI: £213.60 - Net pay £2220.40

In regards to the above, I believe the calculations for my payslips to be correct taking into account my personal income tax allowance of £11500 for the year spread over a 12 month period.

When using the same formula for my partner I get this result for August income tax: £25.20, NI: £213.36, yet her employer has provided them as income tax: £24, NI: £213.60 respectively. Is her employer rounding numbers up and down?

  • 1
    It's probably a subtle interplay between her start date, the date she gets paid and when the "tax free" period runs out. I'd at least wait until you've had a full-month's tax deducted before worrying. Also, I've added a UK tag and changed "insurance" (which is about insurance policies) to "health-insurance" (which – with a country tag – seems more appropriate than the barely-used "national-insurance" tag). You or others feel free to correct if needed.
    – TripeHound
    Sep 21, 2017 at 8:55
  • 3
    National insurance really isn't health insurance. It's not hypothecated in any case, but it's more intended to relate to state pension than state health care.
    – Vicky
    Sep 21, 2017 at 18:25

1 Answer 1


You can use the HMRC calculators to check the figures.

For the NICs, the calculator agrees with you (£213.36), as does applying the formula directly - 12%*(£2458-£680). So I don't know how your employer got their figures.

For the tax, the calculator agrees with your employer (£24). I think a direct calculation actually gives £24.87 - 20% * (£4916 - £11500*5/12). However the tax tables used to calculate each month's tax do involve some rounding in various steps of the calculation (see this other answer on the subject), so it's probably some effect from that.

I'd expect it to look right next month (month 6) because the allowance so far will be a whole number of pounds, or at least by the end of the year. If you really want to step through the details, there are also manual instructions at the link above.

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