[cstejerean]

You can follow a model similar to say hotels, where they auth the card for the room charge + expected incidentals, and then charge for the actual amount at the end of the stay. The amount you capture can be less than the amount you authorized.

[dminor]

> The amount you capture can be less than the amount you authorized.

The amount you capture can also be more than the amount you authorized, but how much more depends on the bank and is not known until you try.

[jtdowney]

It actually depends on the merchant category code (MCC) of your merchant account when it is setup. Only certain category codes, such as hotels and gas stations, are allowed to capture for more than they authorize.