Hii

List of Documents for Verification given below -

• Three Passport Size Photographs identical to the one Uploaded in JEE Main 2018 Registration
• Provisional Seat Allotment Letter
• Candidate Undertaking
• Proof of Fee Payment by e-challan or Internet Banking of SBI for Seat Acceptance
• Photo Identity Card
• JEE Main 2018 Admit Card
• JEE Main 2018 Score Card
• 10th Standard Mark Sheet or Date of Birth Proof
• 12th Standard (or equivalent) Mark Sheet and Pass Certificate
• Medical Certificate
• Category Certificate (if applicable)
• PwD Certificate (if applicable)
• OCI Certificate or PIO Card (if applicable)
• Registration and Filled Choices for Seat Allotment

All the best.

It is better to provide all the required documents at the time of registration.but if you don't have your character certificate it wouldn't affect your admission.