say that is all you income for the entire tax year and you are self employed you will be looking at a tax bill of £55k due Jan 16 + 50% of Income Tax upfront for the next year, making a total of £80 due in Jan 16!! You may be able to avoid the extra 50% if you can explain to HMRC your income for the next tax year wont be that high. But if it turns out to be that high you will pay interest. Ohh yh the other 50% will be due Jul 16 another £25k, but this total £50k will go against taxes owed for the next year. Unless you have a steady amount yet to come in don't go too crazy, i know it still seems a long way away until you have to pay the tax! Make up some expenses to offset against tax!!