@NewJobityJob I can see this is pickling your brain. See if this makes sense for you -
(For simplicity, let's say you earn exactly £46k and MI is exactly £5k.)
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John earns £51k per year (£46k plus £5k). His tax code is the standard 1257L.
This means he pays 20% tax on earnings from £12,571 to £50,270 and 40% tax on earnings from £50,271 to £125,100.
On a salary of £51k, he would be taxed:
20% on £37,699 (£50,270-£12,571)
40% on £729 (£51,000-£50,270)
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You earn £46k and receive £5k of medical insurance.
Your tax code is reduced by £5k to 757L.
This means you pay 20% tax on earnings from £7571 to £45,270 and 40% tax on earnings from £45,271 to £120,100.
On a salary of £46k, this means you are taxed:
20% on £37,699 (£45,270-£7,571)
40% on £729 (£46,000-£45,271)
It is exactly the same. 🤗