Unexpected circumstances can often befall us, and in accordance with Murphy's Law, at the worst possible time.
If you think you're gonna be late, or fear you're gonna be late, call the creditor BEFORE you are late. I think it's best to just be honest with them. Employer changed payday cycle, unexpected medical or school expense, forgot and/or failed to account for this debt this month, or whatever.
Ask whether they have a grace period. This can be heaven sent.
I remember 3 years ago when GMAC screwed up the change of banks for the automatic draft of my car payment. They screwed up. Not me. I faxed them a copy of a voided check and a request to change banks for the draft, and they transposed the numbers in either the routing number or account number. The dingdongs didn't think to call me when payment didn't go through, and they had both my home and work numbers. I was a bit freaked, and I asked about credit reporting. They said not to worry. They sent out a notice when it's 10 days late, and they don't report it late until it's 30 days late. We were only at about day 12.