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Here is an article that I would recommend going through when experiencing this issue.
Devices using iOS 7.0.3 or later:
- Go to Settings > Safari > Passwords & AutoFill, then turn on Credit Cards.
- Return to your Home screen and open Safari. If Safari is black or dark instead of white or gray, Private Browsing is turned on. Safari doesn't save account names and passwords when Private Browsing is turned on. To turn off Private Browsing:
- On iPad, tap the the plus + symbol in the upper-right corner of the Safari page, then tap Private in the lower-left corner.
- On iPhone and iPod touch, tap in the lower-right corner of the Safari page, then tap Private in the lower-left corner.
Macs using OS X Mavericks v10.9 or later:
- Choose Safari > Preferences, then click AutoFill.
- Select the "Credit cards" checkbox.
- Open the Safari menu and make sure there's not a checkmark next to Private Browsing. Safari doesn't save account names and passwords when Private Browsing is turned on.
I've saved credit cards in iCloud Keychain, but none of the numbers automatically fill in when I need to use a credit card on a webpage in Safari.This is expected behavior. Tap the credit card field to then have the option to automatically fill in credit card numbers.
- Devices using iOS 7.0.3 or later: When you tap the credit card field in Safari, you will see the option AutoFill Credit Card above the keyboard.
- Macs using OS X Mavericks v10.9 or later: When you click a credit card field in Safari, you will be asked to choose the credit card that you want to use from your iCloud Keychain.