Do I need to pay advance tax on mutual fund gains?

Yes if your total tax liability exceeds Rs10,000 in a financial year. Advance tax due dates: 15% by June 15, 45% by Sep 15, 75% by Dec 15, and 100% by March 15. Missing these attracts interest under Sections 234B and 234C. Salaried employees with TDS mostly covered can skip advance tax.