Daniel, thank you for your prompt reply.
You can earn upto £32,010 a year after your personal allowance of £9,440 before you start paying tax at 40%
This equates to £2,667 net or £3,454 gross per month.
Anything over that would suffer tax at 40% and there is very little you can do about it, I'm afraid.
As you are an employee, your tax is deducted under PAYE.
This may not be the answer you were looking for but these are the facts.
I hope this is helpful and answers your question.
If you have any other questions, please ask me before you rate my service – I’ll be happy to respond.