Derek all employed people(working for an organisation rather than self employed) pay income tax each week/month on their salary, so at the end of the tax year you will have paid what the tax man requires. If you become unemployed you are given a P45 which shows how much tax (and pay) you have earned from the beginning of the tax year to the termination of your employment.
Depending on how long it takes you to find another job (if at all) the P45 allows you to claim back overpaid taxes for the period you were working.
Hope it helps,
Brian.
