Everyone occasionally makes mistakes, even the friendly experienced professionals at your local bank branch. Sometimes, even the technology they use creates errors. When that happens, your bank will make an account adjustment, which may take some time to show up on your account. In some cases, you may have noticed the error and called it to your bank's attention; in others, you may not even realize the error happened until you're checking your bank account online.
When you take your check or cash to the bank to add it to your account, a teller is responsible for verifying the information and making sure it's correctly input into the system. However, over the course of the day, oversights can happen, especially if the information you've entered on the deposit slip is incorrect. The system may also determine after the fact that the check wasn't endorsed, making the deposit invalid. This is especially true of ATM deposits; in those cases, there is no one to verify your information before you drive off. If a check you deposit bounces, you'll later see the adjustment on your account, likely serving as your first indication that you had an invalid payment. This is the most common type of adjustment you'll see, because so many steps are involved in getting money from your hands into the system. Fortunately, they're often easy to correct. However, if you deposited more money than was registered, you may find that you're unable to use your debit card, or auto-payments might come through as insufficient funds. Keep all your banking paperwork so you can dispute any fees that are charged as a result.
You may also see an adjustment if the bank accidentally withdrew funds from your account. Just as human and tech errors can lead to problems with deposits, they can also result in your bank balance suddenly reducing without explanation. If you watch your account diligently, you'll likely discover this early on and be able to contact the bank to alert them to any errors. However, if you see it as an account adjustment, it's likely already been noticed and corrected by the bank. If the amount that remained in your account wasn't enough to cover your pending payments, contact your bank to ensure you won't be charged fees for any overdrafts due to their error. If you notice fees on your account as a result of the error, get in touch and dispute the amount, and you should see it refunded.