Super Finance Glossary Over 10,000 financial glossary terms... Browse by Letter: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Or Enter Search Term: By Author: All Sources Campbell Harvey Internal Revenue Service Finance Globe FDIC Snow Gold CFTC U.S. Census Bureau Search Tips Same-day Substitution Source Same-day SubstitutionDefinition: Offsetting changes in a margin account during the day that result in no overall change in the balance of the account.