A block of hours agreement can be referred to by a number of other terms, such as a block of time, block contract, or prepaid hours agreement. Some client billing agreements involve invoicing upon completion of a project, or on a monthly or other scheduled basis. In most of these cases, the billing occurs after completion of some work. With a block of hours agreement, the company receives payment from a client prior to the completion of work, for a specified price and number of hours.