If you have a bank loan and you have a checking account with the same bank and your checking is overdrawn so the bank closes your account, can they add to your loan?

There is no general answer to this question, since it depends *entirely* on the agreements (e.g. account agreements) you have signed with the bank. If those agreements give the bank the right to do this, they can: for example, one month when the payroll account  for a small  business I was associated with was overdrawn (a new employee was added, but the contribution to the account was not increased), the bank