A sole proprietor is an unincorporated business with one owner. The business income or loss is reported on Schedule C of IRS Form 1040 as part of the individuals Personal Tax Return.
The filing deadline to submit 2021 Personal Tax Returns (which includes Schedule C, for Sole Proprietorship) and to file and pay taxes owed is Monday, April 18, 2022 (for most taxpayers). Taxpayers in Maine or Massachusetts have until April 19, 2022, to file their returns due to the Patriots' Day holiday in those states.
If you need additional time to file your return, you can file a Personal Tax Extension, (IRS Form 4868) by the filing deadline (above) and you will have until October 15th to file your return.