Why coupon codes don’t work, and where real ones come from

How a discount code works

A code is a rule the shop sets up in its checkout: an amount or percentage off, plus conditions. The common conditions are a start and end date, a minimum basket value, certain products or brands only, new customers only, one use per customer, account or address, a country, and “not with other offers”, which often rules out anything already on sale. The checkout only accepts the code when every condition is met.

Why codes fail at checkout

• It has expired, or has not started yet. Black Friday codes often run for a day or a weekend.
• It is for first orders, and the email address or delivery address has ordered before.
• The basket is below the minimum, sometimes only after another discount has been taken off.
• Sale items are excluded. Around Black Friday this is the usual reason.
• It was single-use and someone else has used it, or it was meant for one person and shared.
• It is for another country’s site, or a different shop with a similar name.
• It never worked. Code listing sites collect codes from many places; some were private, withdrawn or made up.
• It was typed wrong: a stray space, or O for 0.

Where real codes come from

The reliable sources are the shop and the brand: newsletter and account sign-ups, the shop’s app, codes printed on receipts or slipped into parcels, the brand’s own social media posts, referral schemes, and student or loyalty schemes the shop runs. Your bank or card provider may run its own offers too. Treat a code from anywhere else as unverified until the checkout accepts it, and never pay or sign up just to see a code.

First-order codes and the newsletters that follow

A sign-up code usually comes with a stream of marketing email, and unsubscribing is not always quick. Read the code’s terms: most first-order codes are one per customer, and the shop can cancel an order that breaks them.

Coupon extensions and affiliate links

Many coupon extensions and deal sites are paid through affiliate links: when you buy after using their link or code, the shop pays them a commission. That is not wrong in itself, but it means the code shown to you may not be the best one available, only one that pays.

The Chrome Web Store’s Affiliate Ads policy (last updated 11 March 2025) says an extension must describe any affiliate programme prominently on its store page, in its interface and before installation, may only add affiliate links, codes or cookies when it gives you a direct and transparent benefit, and needs a related action by you before each one. Its examples of breaking the policy include adding affiliate links when no discount or cashback is given, and replacing an existing affiliate code without your knowledge.

Before installing any shopping extension, read its store listing for an affiliate disclosure and check what it asks to access: “read and change all your data on all websites” is a lot to hand over for a coupon.

A checklist before you pay

1. Is the price lower than the lowest price of the last 30 days? Test it in the real-deal checker.
2. Is the total right after delivery, fees and the code? Look at the final basket, not the product page.
3. Did the code come from the shop or the brand?
4. Does the code exclude what is in your basket, such as sale items or certain brands?
5. Is the shop who it claims to be? A shop you have never heard of with prices far below everyone else deserves a closer look.
6. What is the return window, and when does it start? Add the order to the return deadline tracker.
7. Paying later? Put it on the pay-later planner with your other plans.
8. Will it arrive in time? Check the carrier’s Christmas deadline.