Buying annuity policy from lic by own managed superannuation fund

Employer had set up own managed Superannyation Fund , duly recognized by IT Act and its income is tax exempt.

On superannuation, contribution defined fund lying to credit of retiring employee, is utilized to buy annuity Policy from LIC to pay annuity. Master Policy is in the name Trust Fund with sub account in employee name. But 2% GST is charged and pension value gets reduced.

My query.....is it correct to put purchase price sub to GST? As 15% contribution out of salary is within 27% overall limit and Fund's income is not sub to tax.

Please guide.