Self Assessment is used to report income, gains and reliefs that need to be dealt with through a tax return. Whether you need a return depends on your circumstances, not simply your job title.
Check the requirement
Self-employment, partnership income, rent, investments or gains can create reporting obligations. Being a company director does not, on its own, settle the question.
Use the official Self Assessment guidance and review changes in your income. Where HMRC has issued a notice to file, deal with it rather than assuming a return is unnecessary.
Gather the information
Bring together records for each source of income, tax already deducted and relevant expenses, allowances or reliefs. The return may need supplementary information for particular activities.
Check the submission route and deadline that apply. Keep evidence supporting both the figures reported and claims made.
Plan payments
Payments on account may be required towards a later liability, followed by a balancing payment or repayment. This can make the first substantial bill larger than expected.
If income falls, a reduction may be possible, but an excessive reduction can lead to interest. Review the payment rules before changing the amount.
Correct problems promptly
Amendments and HMRC enquiries have their own procedures and time limits. Retain the records needed to explain the return and seek help with any notice you do not understand.
Check whether Making Tax Digital changes the record keeping or reporting process for your business or property income.