Calculation of advance tax

You have to estimate your turnover, expenses for the year. A proprietor has to pay Advance tax by 15th Sept(30%), 15the Dec, (another 30%[30+30=60] and rest by March.

By the time you have reached Sept month you have a fair Idea of your profits. You can compare the turnover of last year (till Sept) and see the % increase. Then, estimate the profits  after depreciation, add other income(interest, rent etc) and calculate the tax after TDS. Paying regular advance tax saves interest and eases the tension to arrange for funds at the time of filing of returns.