The fact that your bank allows you to use funds that you have deposited in the form of a check on another bank does not mean that the deposited check has cleared. It only means that your bank made the funds available.
If the bank the deposit check was drawn on refuses payment in a timely manner, and returns the check unpaid, your bank has the right to charge the amount of that check back to your account even if you've already spent the money. If that creates an overdraft in your account, you are liable to your bank to repay it.
BankingQuestions.com is a free service made possible by the generous support of our advertisers. Advertisers are not responsible for site content. Please help us keep BankingQuestions.com FREE by supporting our advertisers. When you see an ad for a product or service you may have an interest in, click through to learn more.