A fixed dollar amount, generally in the context of fees or commissions paid for services. For transactions above a certain minimum size, flat dollar fees may be preferable to fees charged on a percentage basis. Flat dollar amounts are usually specified in contracts and thus are independent of transaction sizes.
Flat dollar fees on stock transactions charged by online brokerages have made it much more economical for the average retail investor to trade stocks. For most services, cost-conscious consumers combined with companies competing for their business will usually cause flat dollar fees to replace fees based on a percentage of the transaction's value.