It does require that you be on top of your income thruout the year, periodically reestimating your tax liability and adjusting your withholding if needed. You would want to make sure that you are on track by checking early enough that you can make adjustments thru extra withholding if you need to. Taxes withheld by payroll withholding are assumed to have been withheld evenly thruout the year, allowing increased withholding later to deal with increased tax liability earlier, so all that matters is whether you get within the margin (90%, or more than last year's tax liability, if I remember correctly, but check) to avoid any penalty for underwithholding. This is probably easier than messing around with estimated payments, as long as you have enough withholdable income to work with. But it pays to be on top of your finances anyway, and not giving the government a free loan is one of the ways, since it allows you to pay down debt earlier and save interest. Operating on non-thinking autopilot has its costs.
