Under self assessment, you are obliged to submit a tax return each year. For the tax year (which ends in April) the deadline is October 31 for paper returns or January 31 if you file online. Most people now file their returns online. If you fail to complete by the deadline then you will face a fine.

You are also responsible for paying your own National Insurance and if you are self-employed then you have to pay two types of contribution:

Class 2 – a flat rate payment which must be paid each week unless you are exempt. Normally class 2 contributions are paid in arrears by a quarterly bill every 13 weeks or direct debit every month.

Class 4 – these are paid on profits and gains at or above a set level. These are normally collected by HMRC.

Employees and self assessment

As regards your employees, self assessment means that you must:

Provide P60 forms to employees by May 31 after the end of the tax year

Calculate the cash equivalent of benefits in kind

Provide details of their expenses and benefits in kind ('P11D details') to relevant employees, as well as the HMRC by July 6 after the end of the tax year

A vital feature of the self assessment system is the obligation it imposes on the tax payer to keep adequate and extensive records. This is in case HMRC needs to check the figures in your return.

You need to keep:

Documentation of all your business transactions

All receipts, bills bank statements and cheque stubs to support them up

Make sure your separate your business and personal financial records

These records must be kept for five years starting from the date on which your annual Tax Return is due back.

If you become registered for VAT you will need to keep a record of all the supplies you make. Invoices normally form the basis of your VAT records. VAT records should be kept for a total of six years.

Hiring an accountant

Although called self assessment there is no problem in hiring someone to complete your return. If you do decide to go down this road be aware that:

They will need time to complete the forms and work out the figures.

They can only go on the information you provide. If you forget some important piece of information then it could have a negative impact

Accountants do vary in quality, so it is good to go through the return at some stage to see if you agree with their figures.