1. Your employer can’t force you to go self employed so if you have worked for your employer for any length of time, you may be entitled to a redundancy payment plus any outstanding holiday pay. Contact ACAS for advice if this applies to your situation.
2. You need to complete a self assessment form to cover the period from when you started working as an independent business. So if you were employed until September 30th, you’d start your records from 1st October.
You will have already paid some income tax and NI from PAYE deductions so you can use your payslips to work out what your tax liability as a self employed person will be.