What form is used to know how much taxes you are going to pay that year?

To estimate how much taxes you will pay for the year, you can use IRS Form 1040-ES, which is the Estimated Tax for Individuals form. This form helps you calculate and pay estimated quarterly taxes if you expect to owe tax of $1,000 or more when you file your return. Additionally, using a tax calculator or tax software can help you project your tax liability based on your income, deductions, and credits.