we charge our customers late fees. Should every invoice have a note that there late fee will be added if not paid on time?

The original invoice doesn't have a late fee note; you'll need to add it manually once you send the invoice to your customer, Danuta.

Including a note about late fees directly in the invoice message is an excellent way to protect your business and set clear expectations. See this sample illustration below:

When adding a late fee note, ensure the automatic late fees feature is enabled. It provides transparency to your customers and ensures that they’re fully aware of your payment terms and the consequences for late payments. 

Additionally, you need to turn on invoice reminders or send one manually to tell the customer they’ve incurred late fees. Otherwise, they won’t know how to pay them.

If you need more information or have any other concerns, please let us know in this thread.