An MBA can assist CA in doing tax audit. It is not that an MBA cannot do tax audit work, but a Tax Audit Report is signed by CA only. An MBA is not authorised to sign tax audit report nor a tax audit report is valid if it is signed by MBA.
In India Only qualified Chartered Accountant holding valid Certificate of Practice can only Sign Tax Audit Report.
If you are working with practicing CA then you can conduct the audit work. as said signature on audit report has to be done by CA.
CA Kintal Shah