You can safely assume the second job will be coded BR X and have a flat 20% deducted as income tax.

See gov.uk/tax for official calculators and National Insurance Table.

Your second job will be taxed eg 20%= £15

You will pay tax at 20% on your second job.

Basic TAX rate £11,001 to £43,000 = 20%

so you can earn up to 43k within the same tax bracket ( basic rate )

you also get a Personal Allowance Up to £11,000 = 0% tax rate

so if you earned 24k per year you are only taxed on 13k of it @ 20%

Add the 2 together, minus your 11K yearly allowance and you will pay 20% tax on the remainder.

oh yea, when you add another job, with more money your tax will also be greater