DEFINITION of 'Same-Day Substitution'
An offsetting change in a margin account, made over the trading day, that results in no overall change in the value of the account. When a same-day substitution is made, a margin call is not generated.
BREAKING DOWN 'Same-Day Substitution'
A same-day substitution happens when a rise in the market value of one margin security is offset by an equal decline in another.