As several others have said, there is no limit on a u201clegal amount of moneyu201d someone can earn from a business without getting into trouble with the IRSu2014at least, as long as the business owner complies with the Internal Revenue Code, pays their corporate taxes or self-employment taxes, and files the appropriate returns.There is a Treasury rule that requires banks and business owners to scrutinise large amounts of cash; the purpose of this is probably more to prevent organised crime than specifically for tax collection. Form 8300 and Reporting Cash Payments of Over 10000.If youu2019re looking for the amount you can earn through self-employment and not have to pay Social Security tax or file a Schedule SE, itu2019s $ 400 per year. If you have a u201cregularly conducted business,u201d you have to file a Schedule C; the test for this is whether the activity is systematic.Use Schedule C (Form 1040) to report income or (loss) from a business you operated or a profession you practiced as a sole proprietor. An activity qualifies as a business if your primary purpose for engaging in the activity is for income or profit and you are involved in the activity with continuity and regularity. For example, a sporadic activity or a hobby does not qualify as a business. To report income from a nonbusiness activity, see the instructions for Form 1040, line 21, or Form 1040NR, line 21.2022 Instructions for Schedule C (2022)