The same tests as any business
The FTA's registration rules do not carve out freelancers. If your taxable supplies and imports exceeded AED 375,000 in the previous 12 months, or are expected to within the next 30 days, you must register. Below that, voluntary registration is possible once supplies and imports, or taxable expenses, exceed AED 187,500.
A freelance video editor billing AED 32,000 a project, with one project most months, reaches about AED 384,000 over a year. A software consultant on a day rate of AED 2,500 crosses AED 375,000 after 150 billable days. These are ordinary freelance incomes in Dubai and Abu Dhabi, not exceptional ones.