A more thorough explanation:

A promissory note that is payable on demand means that the person who owes the money has to pay it back whenever the person who is owed the money asks for it. This type of note doesn't have a specific date when the payment is due, but it is usually expected to be paid back soon after it is written.

For example, if you borrowed money from a friend and wrote a promissory note that said you would pay them back "on demand," your friend could ask for the money back at any time. They wouldn't have to wait until a specific date to get their money back.

The exact due date for a note payable on demand can vary depending on where you live. In some places, like Nebraska, the note might be due the day after it is written. In other places, like Alabama, the note might be due as soon as it is delivered.