A bank overdraft can negatively impact your credit score if you do not repay the overdraft quickly because overdrafts are a form of debt. If left unpaid, the bank can report this debt to credit bureaus, which will appear as a negative item on your credit report.
In addition, if you have overdraft protection with your bank, the bank may report this as a line of credit or loan on your credit report, which can impact your credit utilization ratio. Your credit utilization ratio is the amount of credit you are using compared to the total amount of credit available to you, and it is a factor that credit bureaus consider when calculating your credit score.