When working out your daily rate, keep in mind that your former employer incurred extra costs over and above your gross salary, and these costs will now have to be paid out of your fee income. They fall into four categories:
You should be realistic about the number of days in the year that you are likely to work. Having done the calculation, you also need to be realistic about the fee you intend to charge, particularly if this is your first assignment and you have yet to prove yourself.
As a starting point, you might choose to start with your latest gross salary. To that you should add all the extra costs outlined above, and then divide the total by the number of days in the year that you anticipate working in order to arrive at a daily rate. You could refine this by producing one rate for short assignments and another for longer assignments where the number of days is more or less guaranteed.
Above all, remember that your daily rate includes an amount that will be used to pay Employer’s NI contributions, and in negotiations you may need to point out to clients that whilst they will not be paying Employers NI on top of the fees they pay you, it must instead be paid by you out of the fees they pay you.
Be quite clear about how much of your daily rate will go to you and how much will be paid as tax and NI, as it is counterproductive to grumble about it later on! As a guide, taking the year as a whole, you might expect that just under half of the total amount you devote to payroll will go to HMRC as tax and NI (Employee’s NI and Employer’s NI). Obviously, however, the more you earn the more tax you will have to pay.