1.by the end of the year, how to I prove or input that I paid such an amount if I use turbotax software?
First, you can't use TTX to pay quarterly taxes with. But you can most definitely pay them on line at www.irs.gov/payments. Upon making the payment (I can't stress this enough) *PRINT* *YOUR* *RECEIPT*. That is your "proof" you made the payment.
2. Do I need to file any tax document quarterly when I am paying the tax online? Or can I just submit the payment?
No. But as stated above, when you make your online payment *PRINT* *YOUR* *RECEIPT*. When it comes to dealing with the IRS, if it's not in writing, then it did not occur. Period.
You'll be able to enter your quarterly payments in the TurboTax program while entering your data. You'll deal with that under the deductions and credits tab in the Estimates & Other Taxes Paid section of the program.
Note that if your state taxes personal income, you will need to pay your state quarterly taxes separately from your federal quarterly taxes. How you do that, depends on the specific state. So you'll need to check your state's department of revenue or department of taxation website for how and when quarterly state taxes are due.
