Read the message before changing the basket

Copy the wording or take a screenshot of the checkout message. ‘Not valid for these items’ points towards product exclusions; ‘minimum spend not reached’ suggests a threshold. A generic ‘invalid code’ message provides less information, so open the offer terms rather than guessing what the shop means.

Check that the characters match the original offer. Remove a trailing space introduced when copying a code. If a code appears in a retailer email, use that email to check its spelling and conditions. Repeatedly submitting different guesses rarely tells you more than the original terms.

Count only the items that qualify

The displayed basket total may include excluded brands, delivery or products already reduced. An offer can use a narrower qualifying subtotal. Look for the wording that defines eligible spending and check each line against it. Do not assume the largest total on the screen is the number used for the voucher.

For example, imagine an offer requiring £50 of eligible full-price clothing. A basket containing £42 of qualifying clothing and an £18 excluded gift card would not reach that threshold, despite showing £60 before delivery. Those figures are an illustration, not an offer from a particular shop.

Match the offer to the account and channel

Some offers are restricted to new customers, selected accounts, a particular country or orders placed through an app. Check whether signing in is required and whether the email address receiving the offer is the one used for the purchase. A code shared by another shopper may not be transferable.

Read any expiry time as well as the date. When the terms do not specify a time zone or the code seems to have stopped early, ask the shop to clarify. Avoid creating extra accounts or changing personal details to get around a restriction; that does not establish that the order qualifies.

Look for an existing discount

A sale price, automatic basket offer or previously entered voucher can prevent another code from applying. Compare the checkout both ways if the shop allows you to remove the existing offer. Record the final total, including delivery, rather than comparing headline percentages alone.

If the code still fails after these checks, send customer support the code, the relevant offer terms and the product names. Do not share card details or passwords. Keep the basket only if its price makes sense without the disputed saving. An unnecessary extra item is still a cost, even when it makes a voucher work.