The turnover test
The FTA natural person page sets two conditions: the person conducts a business or business activity in the UAE, and turnover from those activities exceeds AED 1 million within the calendar year, January to December. Turnover means gross business receipts, not profit, so a designer who invoices AED 1.1 million and keeps AED 400,000 after costs has crossed the line.
The FTA excludes three kinds of income from the test: wages, personal investment income and real estate investment income. An employee who also rents out a flat in Dubai Marina in their own name is not running a business because of that rent.