There's an option to disable all autofill in settings. Does that help? Detecting whether a card is credit or debit requires sending the card number to bank servers, which is the opposite of what you want, I think.

Unfortunately not. I rather like auto fill and want to keep it, but I just
don't want it saving my bank information. Surely though there are
algorithms that can detect credit / debit card details locally though....?

Local detection of credit/debit is impossible, unfortunately.

In which case I wouldn't mind it being sent to a server strictly for
checking purposes, so long as it's not stored.

I'm curious though. Are all numbers sent to Google for checking if local
checking is impossible?

No. Chrome sends the CC to Google only if the user clicks "Approve" on the dialog that prompts to "Save card to Google Account." You can manage this data in https://payments.google.com.

To butt in on this conversation, I think starbeam is talking about identifying card data vs other data, which chrome already does. I don't think there is the expectation that chrome will handle debit cards differently than credit cards.

This is likely another request similar to many other tickets that have been opened over the past 5+ years to get Chrome to stop asking to store card data without having to turn autofill completely off. I don't know why this is such a terribly difficult thing to do, and it causes huge issues for businesses that process customer credit cards that will be out of compliance if their users accidentally click yes.

 Issue 800777  has been merged into this issue.

This is asking for disabling credit card autofill functionality, basically. Duplicating into the other feature request.