This is a question that we are asked all the time by clients who are new to self assessment.
It is difficult to say what you actual liability will be until your year end is past and we have all the information as to your income and expenditure and its nature, as some will be allowed for tax purposes whereas others wont.
If you want to have a rough indicator a good guide is HMRC’s Ready Reckoner. Although it will not give you the figure to the penny it will give you a good idea so you can plan ahead for your tax liabilty.
Remember that for year ends that fall in tax year 2013/14 (6 April 2013 – 5 April 2014) you are due to submit your tax return and pay any tax by the 31 January 2015.
There are special rules to what period will be taxed in your first few years of business and it is always best to ask as each case is different.