Overpaid PAYE tax & refund, how does that work?

Dear HMRC team, I'm having some difficulties trying to resolve overpaid PAYE tax issue. As 23/24 tax year began I received one-time lump sum payment (£19,513.30). My salary is May will be £0 (been fired). My 23/24 April payslip shows the tax deductions of £7,159.50. My tax code is 1257L. I don't understand why I own so much tax even though the tax year just began? Even if I apply 20% tax bracket on top of £19,513.30 I will get £3902.66 in taxex, not £7k+ My question is: 1) What tax rate has been applied to my income in 23/24? 2) Why I was put into the next tax bracket in 23/24? 3) How do I claim the overpaid tax? 4) When can I expect the refund to be made given that I don't know when I find a new job? Best wishes, Petr

Hi
If a payment was made in April, you would only be entitled to 1/12 of the tax free allowance for that period.
This would also mean that you would pay 40% and some 45% tax on the income.
If you have not started a new employment within 35 days you can submit an online P50 form to request a refund.
Thankyou.