Not everyone needs to make estimated tax payments. For example, if you are an employee, you do not need to make estimated tax payments because your employer withholds taxes from every paycheck and sends the money to the government for you. This way, you pay your income taxes as you go.
But if you are self-employed, estimated tax payments are the IRS-mandated method of paying income taxes as you go. Estimated tax payments are due in four quarterly installments (although not every quarter is three months long):
1st quarterly tax payment due date: April 15th 2nd quarterly tax payment due date: June 15th 3rd quarterly tax payment due date: September 15th 4th quarterly tax payment due date: January 15th