Tax and NI contributions on a bonus

[hmr1]

Hi - I am due to receive a bonus of £2500, which will be paid seperately from my monthly salary.
My tax code is 647L and my total cumulative gross is 28730.70 with the cumulative taxable gross being 29175.70, can you tell me how much tax and NI I will pay on this?

Thanks

[factor-fiction]

Your marginal rate of income tax is 20% and your marginal rate of NI is 11% (or 9.4% if contracted out. The total tax/NI rate is therefore close to 30% so you'll be deducted close to £750.
It may or may not all be deducted in one go depending on the timing. Will it be paid in March?

[hmr1]

Yes the payment is due in March a week before my usual salary payment.

[factor-fiction]

Well it should be close to £750 then based on the applicable marginal rates, although there may be some other year-end adjustments depending on whether you had paid right amount of tax in previous months.
Enjoy.

[hmr1]

Thanks very much for your help redhelen and factor30, can I just ask how you came up with a total of £200 difference?

[factor-fiction]

I took 30% as your marginal rate of tax/NI. The actual amount will be between £735 and £775 depending on whether you are contracted out. I'm confident I'm correct but am happy to get other ideas.
I don't know how redhelen arrived at her figure- maybe she just applied average tax rates rather than the marginal rate.

[Skyline D]

Factor 30 is fundamentally correct but in practice your March allowances will presumably be allocated to the bonuses since it's being paid first and you'll pay less tax on it than he says directly. You'll pay more than usual on your normal pay the week later though because it will all fall to be taxable with no exempt band.

So although the mechanics won't be as obvious as factor implies, he's more correct than Helen. She'll probably be more correct on what actually comes off the bonus payment though.

I hope that was clear!