Clear Checks You Write
It can take a while to clear checks. Once you write the check, you should act as if the money is no longer in your account. However, it may take days (or longer) for the money to actually leave your account. During that time, the check is said to be "outstanding". Using the money in the meantime is called "taking advantage of the float".
Clear Checks You Receive
When somebody writes you a check, it "clears" when the money hits your account and you can spend it. However, you can get into trouble - even if you think they cleared the check.
The bank is required to make at least part of your deposit available to you, and they might even assume that the check is good and you can use all of the money. Convenient, right?
If the check bounces, you’ve got trouble. The bank will take the money back, and if you’ve already spent the money you’re responsible for paying the bank back.
Dangers of "Cleared" Checks
If you have any doubt about a "cleared" check, don’t spend the money until you’re certain that your bank has collected the money it needs. You can call your bank and ask whether or not they’re 100% certain the check is good, and if there is any risk in using the money.