Most address bugs are predictable. The same ten mistakes show up in checkout, signup, and shipping forms across industries.
The mistakes
Check these before you ship a new address form.
- Forcing a US state dropdown on every country.
- Rejecting a five-digit ZIP because ZIP+4 is missing.
- Treating a postal code as a number and dropping leading zeros.
- Putting the apartment number in the city field.
- Requiring a street suffix for rural routes.
- Rejecting APO/FPO addresses.
- Using one “State/Province” label for every country.
- Copying the shipping address into billing without showing it.
- Putting the full address in a URL or analytics event.
- Claiming that a format check proves delivery.
The fix
Make the country the first field, adapt the labels and validation, keep postal codes as text, and test one address from each supported country before launch.
A quick regression test
Use a generated address for each country, fill the form, save, reload, export, and re-import. If a field changes shape, you have found the bug.
Questions
- A billing-address mismatch can decline a payment. A postal-code leading zero can break an export. Both are easy to prevent.
- Only if delivery accuracy is critical. Format validation and a good manual path cover most consumer forms.
Which mistake is most expensive?+
Do I need a full address-verification service?+
Examples are synthetic. Do not use a generated address for identity checks, account registration, or delivery.