is registration is mandatory or not for small TRANSPORT agent

If your turnover is below threshold limit 20 lac as per section 22 CGST Act , you dont need to obtain Registration

NO

Agree with Pankaj Sir...

As per the Provision of Section 22 of the CGST Act 2017, a person needs to get registered under GST only if his Aggregate Turnover [ computed u/s 2(6) of the CGST Act 2017 ] exceeds Rs. 20 lakhs.

Since your Turnover is less than the prescribed Turnover limit ( i.e. Rs. 15 lakhs), you don't need to obtain Registration under GST.

However, you can Voluntarily Register under GST for enjoying the benefits of ITC and thereon as per the Provision of Section 25(3) of the CGST Act 2017.

EXTRACT from the Act :

SECTION 25(3) : "A person , though not liable to be registered under section 22 or section 24 may get himself registered voluntarily, and all provisions of this Act, as are applicable to a registered person, shall apply to such person."

Regards.