When you save credit card details, you provide fields for the contact data for the card issuer. But there is no place to save the billing zip code. For example, I saw a form on www.indiegogo.com that was like this:
CARD NUMBER | EXP DATE | CVV | ZIPCODE
All 4 fields in a box. On one line. And the field names we in faint, dimmed out grey against a white background and didn't turn black until entries were made in the CARD NUMBER field. So I never even noticied the field named ZIP in that box.
I went so far as to complain to the company because I couldn't make a purchase. i was majorly frustrated. The form on the page only had the typical multipe field SHIPPING ADDRESS which isn't where my bank cards are billed, that is my mailing address, which is different than my shipping address. But there was no similar series of fields for Billing Address.
To process a card transaction, the only thing really needed is an AVS Match. Address Verification System. So merchants only submit the billing zip, which results in a marginally higher merchant fee, but makes more transactions get approved instead of abandoned
I added a field called ZIPCODE in the credit card 1Password database after card number, expiration date, and CVV for automatically adding the billing zip code but I think it should be built into the product and tested. If there are multiple fields for a billing address, then let the user choose to fill that in from identities. But if there is not multiple field billing address area, start looking for that ZIP field around the card number and fill it from the credit card record.
I am not sure my adding ZIP will allow 1PASSWORD to fill it every time, no matter what they call it, be it ZIP, ZIPCODE or BILLING ZIP or BILLING ZIPCODE. And to differentiate it from other ZIP code fields on the page.
This is not the same ZIP CODE as the card issuers mailing address.
Anyway, since this threw me for a loop and wasted a bunch of my time, I thought I'd present it here. It's just a thought. Have a good day.