In the following scenarios would an ECOA AAN be required?:

We do not receive proof of hazard or flood insurance on the property securing the HELOC so the line is frozen.

Credit card accounts are closed due to past due status.

Or is a letter just basically stating that the account was frozen or closed with the reason all that is needed?

IF the loan is currently in default and you are taking actions based on that fact, that is not adverse action.

Thanks

Or is a letter just basically stating that the account was frozen or closed with the reason all that is needed?

If you suspend or terminate a HELOC there are specific monitroing/notification requirements, outside of ECOA, found in 1026.40 and 1026.9.