To avoid interest and penalties, you must make sufficient federal income tax payments long before your April filing deadline through withholding, estimated tax payments, or a combination of the two. The third 2018 estimated tax payment deadline for individuals is September 17.
If you don’t have an employer withholding tax from your pay, you likely need to make estimated tax payments. But even if you do have withholding, you might need to pay estimated tax. It can be necessary if you have more than a nominal amount of income from sources such as self-employment, interest, dividends, alimony, rent, prizes, awards or the sales of assets.