No it is not required bayou to submit your gap certificate at the time of registration in GPAT which is conducted by National testing agency. Other than this I am mentioning below the name of all the documents which are required at the time of registration for GPAT:

• Marksheet and certificate of the qualifying examination
• Category certificate if you belong to reserved category
• Transfer certificate and migration certificate
• GPAT admit card
• GPAT score card
• Your passport size photographs

Other than this you are required to carry an identity proof of yours at the time of appearing at the examination centre of GPAT. The identity proof can be PAN card, Aadhar card, voter ID card.

At the time of applying for GPAT you are required to pay an amount of 2000 rupees. FOR FEMALE CANDIDATES the applying fees is 1000 rupees.

Read More about GPAT: https://www.google.com/url?sa=t&source=web&rct=j&url=https://pharmacy.careers360.com/exams/gpat/amp&ved=2ahUKEwih94qu4oD1AhVX9nMBHcneDPkQFnoECAMQAQ&usg=AOvVaw0ma4M0bAZwoxCAx7j4KbA7