I dunno, I pay taxes on revenue.

Are you a company? If not, then you probably don't have revenue -- you have income.

In the US, unless you are a C Corp then you probably also pay taxes on net income of some form. C Corps have some different accounting, where dividends are double taxed unfortunately.

Small business owners are very impacted by the R&D schedule.

If only I can pay tax just for income - expenses (rent, food, etc.)

Do you take a standard deduction?

It's clearly not enough to cover all of the expenses that are required to generate your "revenue", but it's a gesture in that direction.