Science doesn't always wait for the arrival of money. If you have received a notice of award, and then the funding is delayed, you may need to open an "early account."
For example, if you have a graduate student who is already working in this area, and you need to support him on a Research Assistantship, you may open the project account before the funds arrive. To do this, you need to complete a form (this link will open the OSR "PTA setup" page, select the "Early PTA Request Form," OSR Form 38).
The "early account" form asks for a department guarantee account, in case the expected funds do not materialize.
When the funds arrive, they will automatically go into the project account, and no transfers will be necessary - a significant advantage over placing these costs somewhere else and transferring them later. If the funds are NOT forthcoming, then those costs will be charged to the guarantee account.
Some sponsors prohibit ANY preaward costs, while others limit such costs to a specified amount of time. For example, costs that are incurred more than 90 days before the start date of a project may be identified as unallowable. Be sure to check the terms and conditions of your particular award for these types of restrictions if you are considering an "early account."
The Office of Sponsored Research has published additional information on this subject.