SSC CGL Tier-1 is a screening test with four sections and 0.50 negative marking per wrong answer. Tier-2 has a compulsory Paper-1 for all posts and an additional Paper-2 for specific posts like JSO. Negative marking is higher in Tier-2. The final merit is based on Tier-2 marks, while Tier-1 only decides shortlisting. Always confirm the scheme from the official SSC notification.