Important:
This answer is based on tax law for the tax year ending 28 February 2020.
Answer:
Under paragraph 3 of the Sixth Schedule to the Income Tax Act, a “person does not qualify as a micro business for a year of assessment where—
(f) in the case of a company—
(i) its year of assessment ends on a date other than the last day of February;”
The next problem is that, under paragraph 8(1), a “person that meets the requirements set out in Part II may elect to be registered as a micro business—
(a) before the beginning of a year of assessment or such later date during that year of assessment as the Commissioner may prescribe by notice in the Gazette; or
(b) in the case of a person that commenced business activities during a year of assessment, within two months from the date of commencement of business activities.”
The legislation therefore does not allow SARS to do what you suggested (retrospectively register).