How to use a promo code at checkout
A promo code is a short bit of text you type in at checkout to get something off your order. It might be a percentage off, a fixed amount, or free shipping. Some shops call it a coupon, a voucher or a discount code, but they all work the same way.
It sounds easy, but people mess it up all the time, usually because they paste the code in the wrong place or at the wrong time. Here's how I go about it.
Step by step
First, add the items you want to your cart and go to the checkout or cart page. Most shops only show the promo box once you're in the cart, so don't panic if you can't see it on the product page.
Next, look for a box called something like "Promo code", "Discount code" or "Coupon". Sometimes it's hidden behind a small link, so you may need to tap it first. Paste the code in exactly as you copied it. Extra spaces at the start or the end are a very common reason for an error.
Then press Apply and check that the total actually went down. Don't assume it worked just because there's no error message. Look at the final price before you enter your card details.
What if there's no code to type?
Some deals just need you to follow a special link. If a deal says "no code needed", the discount should show up automatically when you shop through that link. If you open the store in a different tab or from an ad later, the offer may disappear.
Quick tips
Check whether the code is for new customers only. Check the minimum spend, because many codes only work above a certain amount. And check the country, since some codes are limited to certain regions. If one code fails, the shop's terms usually explain why.
For more on that, read why promo codes fail.