Considerable, under self employment you pick your own accounting date, the last day of the month you wish it to be. The amounts declared for tax are then [source: Ward Goodman]:
Begins with the date the trade starts and ends with 5 April of that tax year
2 Accounting period ends in Year 2 - if the period is less than 12 months 12 months from the date the trade starts -
if the period is more than 12 months 12 months ending with the accounting date -
if the period is 12 months 12 months ending with the accounting date
Accounting period does not end in Year 2 6 April to 5 April of that tax year
3 Continuing business 12 months ending with the accounting date
You will immediately see that under this system the same income can be taxed twice in different years; this is known as overlap and should be carefully recorded. Overlap relief can be claimed at any time, but many traders keep it until they cease to trade.
I do hope that you have found my reply of assistance.