When should my friend file income tax?

This discussion clarifies income tax obligations for a self-employed IT professional with an annual income of approximately £875,000. It addresses the crucial deadlines for filing income tax returns, which is typically by 31st July following the financial year. The conversation also delves into the necessity and timing of paying advance income tax, explaining that it's required if tax liability exceeds £10,000 and no TDS is deducted, with instalments due throughout the year, including before March 15th. Finally, it touches upon the estimated income tax payable based on tax slabs, even after considering investments like those under Section 80C.