TabKeeper is a free utility designed to keep track of "tabs" of money owed. It was originally designed to help ease the confusion of sharing bills with roomates and also keep track of all bills in one place. TabKeeper can easily be used to keep track of business-related invoices.

TabKeeper Features
Automatically Saves Current File upon exit.
Optionally Logs every tab deletion.
Quickly change color schemes to make program more exciting.
Keep track of infinite tabs with linked list architecture.
Free Updates, feature requests