A student can be up to 30 minutes late for their remote (at-home) exam proctored by ATI. However, if you are taking an exam proctored by an institution, you may not be able to start the exam late.
A tester has up until 30 minutes past their exam start time to join their TEAS at ATI exam. Any time after that, they will have to register for another attempt and may not be allowed to test that day.
If a student is taking an exam that is proctored by their institution (TEAS online at Institution), a student may not be allowed in late. Schools and testing centers that proctor their own exams each have set their own testing requirements such as late arrival, number of attempts, and more. It is important that you check with your institution to understand their testing requirements prior to taking your exam.