I have been on Jobseeker's Allowance (JSA) for around 12 months and have recently managed to find a job. Will I have to pay tax on my earnings intially and then claim the tax back or will my weekly wages be adjusted automatically? I didn't have a P45 but I have completed a P60 and handed that to my employment agency.
The official HMRC line is ....
''When you stop claiming jobseeker’s allowance to start work for a new employer, the Benefit Office will check the amount of tax paid against your taxable income including the amount of jobseeker’s allowance you've received. They will refund you any overpayment and issue a P45(U) which you should give to your new employer''.
So you should have had a P45U but as you say this wasn't the case.
In theory your new employer should adjust your PAYE tax code (using the information on the P45) to ensure that you pay the correct amount of tax automatically going forwards (taking into account what you have paid so far this tax year). So given your concerns it is important that when you get your first payslip that you check your tax code is correct. Read my article - Money tip #4 – Check your tax code in which I explain how to check and what to do if you are over taxed by your new employer.
I hope that helps
Money to the Masses