This post on How to buy waec verification pin online provides answers to the question: what is waec verification pin?
WAEC VERIFICATION PIN is a means of verifying candidate’s information electronically. This is not for reducing of your age. WAEC VERIFICATION PIN is a pin used to verify the age you provided to WAEC during the WAEC registration. This means that why JAMB or your institution provides NYSC with your date of birth, there might be discrepancy in your real age which can be verified with the WAEC VERIFICATION PIN.