Why is a valid UK zip (postcode) failing so payment not going through?

[Vonnie]

Is this my store or the customer?

Currency gbp Failure code incorrect_zip Failure message The zip code you supplied failed validation

This is what I see from abandoned checkout... the postcode IS a valid one as a longstanding customer before my shopify site.

[Victor]

Hi @Vonnie,

Thanks for getting in touch. This error usually occurs when the postcode or ZIP code the customer has entered does not match the one that is on file with their credit card company. When the information is submitted to the cardholder's bank the discrepancy means verification cannot be completed and the transaction fails as a result.

This is part of our Address Verification System (AVS) that you can enable when configuring Shopify Payments, and is a fraud prevention measure. I would recommend informing the customer that their checkout is likely failing due to this reason and that they should check that the postcode they are providing matches the one on file with their bank.

[RallyRaid_Liz]

we are having the same issue, after checking the post code supplied is correct, but payment is still not going through

[Victor]

Hi @RallyRaid_Liz,

Are you using Shopify Payments or a third-party payment provider to accept credit card payments? What error message are you seeing in the abandoned checkout timeline, if any?

[RallyRaid_Liz]

We are using shopify payments, the message that shows is "invalid zipcode"

[Victor]

Hi @RallyRaid_Liz,

Is this order one that contains a UK address? If so, where in the UK is this zipcode (e.g. England, Scotland, etc)? Do you have all countries and regions in the UK enabled in your shipping settings as shown below?

[chris_morris]

Hi @Vonnie,

This issue usually comes down to how the payment gateway validates the postcode (ZIP code) — and you're right, it’s often frustrating when perfectly valid UK postcodes are flagged as incorrect.

Possible Causes:

1. Formatting mismatch
   Some payment gateways are sensitive to spaces or case in the postcode (e.g. "SW1A1AA" vs "SW1A 1AA"). If the customer enters the postcode in an unexpected format, it can trigger a mismatch.

2. Card issuer AVS check
   Some card providers use Address Verification System (AVS), and if the billing address postcode doesn't exactly match what's on file with the card issuer, the transaction can be declined — even if the postcode is valid in general.

3. Third-party gateway settings
   If you're using an external payment provider (e.g. Stripe, Authorize.net), their internal postcode validation rules may differ from Shopify’s checkout expectations.

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 A Smoother Alternative: WallidPay

If you’re experiencing ongoing issues with postcode validation — especially for UK customers — you might want to try WallidPay. It lets customers pay directly from their UK bank account, with:

• No postcode or card checks — no more zip validation errors.

•  Secure bank-authorized verification.

•  Instant, account-to-account payments with all major UK banks.

•  Lower fees and fewer abandoned checkouts.

You can check it out here if you’re open to adding a seamless, postcode-free option at checkout.