The process keeps changing time to time.
in the earlier process, you have to seek a special approval from Ministry of defence which used to take approximate one month and then submit payment at depot and to collect purchase order.
but under the new process now you have to signup at afd.csdindia.gov.in using your canteen grocery card, PPO certificate number and other KYC details.
The signing up process is usually approved by admin first which takes a few days (as on 05 jan 2021).
after signing up you have to upload your documents like pan card, Adhar card, payment details and availability certificate etc and then submit the copy of these documents to an authorized canteen (authorized canteen can be checked with the dealer).
The canteen takes 7-15 days(or may be more) for precuring purchase order from the depot.
under the new process you don't have to personally visit the depot.
Eligibility for purchasing a car through csd has also changed recently.
Here is notification for more details.
Thanks for reading .
