How much time do you have to file your income taxes?

Filing and payment are 2 different things. You must pay your estimated tax, through withholding or filing a 1040-ES with payment (quarterly), during the year, or face penalties and interest when you do file/pay. Returns are due by April 15. Any remaining payment is due then too. However, as long as you're paid in, or make that 4/15 payment, getting a 6 month extension of time to complete the forms is automatic and easy.