Merchants are experiencing an issue where checkout pages automatically pre-fill incorrect postal codes for new customers. The codes appear to be based on IP address geolocation but are consistently wrong, with many ending in “1AA” and sometimes directing orders to completely incorrect locations (one example: Buckingham Palace).
Root Causes Identified:
Shopify support indicated they recently switched from Google’s address autocomplete system to their own proprietary system, which may have caused the errors
One merchant traced the problem to a shipping calculator app that generates random postcodes based on IP addresses in the cart, which then incorrectly carries over to the checkout address form
Current Status:
The issue remains unresolved for some merchants despite Shopify investigating for approximately one month. Affected stores have disabled address autocomplete as a temporary workaround. Merchants are particularly frustrated this occurred during Black Friday week, the busiest retail period.
Summarized with AI on November 2.
AI used: claude-sonnet-4-5-20250929.
I’m wondering if anyone can shed light on this please? Shopify support have been looking into this for about a month now, and have not been able to resolve it.
Every new customer who lands on our checkout page, get’s their post code box pre-filled with a random incorrect post code, it looks like it’s tried to find them via i.p address, but it’s always a random post code absolutely nowhere near the customer, and the last part of the address is always 1AA.
One of the orders (and this was actually dispatched too) went to Buckingham palace!
I found somewhere in the theme where it’s possible to turn on auto pre-filling of addresses, but this isn’t turned on, we have no idea what’s going on, neither does shopify apparently.
Our store has been suffering the same issue. Lots of auto-completed postal codes are being populated incorrectly. I’d love to hear from Shopify as this is their checkout issue.
Shopify chat support revealed that they were using Google for their address auto complete and are now switching to their own Shopify system for auto filling address fields. That explains why we’ve been seeing so many incorrect postal codes for customer orders. I’m stunned at the disregard shown by Shopify, does it make sense for Shopify to do this at the busiest week for retail sales, Black Friday week? Shopify didn’t take this into consideration. We have now turned off address auto-complete in our checkout.
I have been having this issue recently and have just fixed it by removing the app I had to calculate shipping rates in the cart. The app would generate a random postcode based on the IP to give customers an idea of shipping costs before they reached checkout. The app for some reason has started to then auto fill this random postcode in the customer’s address form.
Great app but caused us lots of problems with postcodes so we have now disabled it.
