Hello, Powder Blue Panther , and thanks for giving YNAB a try (or thinking about it!).
YNAB will never, ever ask for your checking account number. If you choose to use Direct Import to download transactions, YNAB will ask for your bank login credentials. We never retain that information, but we do pass it on to our Direct Import partners, who take industry-leading security precautions with it.
In short, we take your privacy and security extremely seriously, and never ask for, retain, or share information beyond what's necessary to make the software work best for you. More information in our Security Policy.
Please let me know if you have any other questions!