Why Does A Plastic Bag Help With A Credit Card?

By Bruce Boswell •  Updated: 12/14/21 •  5 min read
Filed under: Credit Cards

Whether you’ve recently become a cashier and one of your colleagues has recommended that you keep a plastic bag handy in the case of an emergency, or you’re stuck with a buggy credit card and are looking for a quick fix – then you might have heard about the plastic bag trick.

Just picture it: you’re at the cash register preparing to pay for your groceries, only to discover that after a few swipes of your credit card the transaction isn’t going through.

Why does a plastic bag help with a credit card

The cashier reaches over and quickly wraps your card inside a nearby plastic bag and, almost like magic,  your credit card works perfectly…but how did the plastic bag manage to fix it, exactly?

Whether you want to know how to get a credit card working in an emergency or you’d simply like to learn a little more about this unique method, rest assured that you’ve clicked on the right article.

To help you learn more about this trick, read on for some more information on how a plastic bag is able to help get a faulty credit card working again. Let’s jump right in! 

What Is The Plastic Bag Trick?

If you’ve never heard of the plastic bag trick, then before we go any further we’re first going to take a moment to talk you through what it actually is.

A quick-fix method most commonly used at restaurants and retail stores, the plastic bag trick is a simple yet effective way to help fix a buggy credit card (and even sometimes debit cards) and get it working again so that a transaction can be successfully made. 

While little is known about how the plastic bag trick came about, it’s a method that is common knowledge throughout stores across the world!

So, regardless of whether you’re a retail worker that wants to know all the tricks of the trade, or you simply want to be prepared in the instance that your credit card doesn’t charge when swiped – the plastic bag method is a great trick to keep in mind.

When used correctly, it just might be able to get your card up and running as normal again so that the charge can go through, and you won’t have to leave the store empty-handed. The only question is, how does the plastic bag trick work? This brings us to our next section.

How Does The Plastic Bag Trick Work?

Even though it might seem a little bit like magic, there’s actually a very simple reason as to why plastic bags are so effective at getting buggy credit cards to work as normal.

To cut a long story short, if you take a look at your current credit card, you will see a black stripe running all along the back of the card. This black line is made up of a variety of teeny tiny little magnets that have been wrapped up tightly in a plastic coating.

To ensure that the credit card is able to effectively work and make transactions, these tiny little magnets are innovatively grouped into non-magnetic areas and magnetic areas, and the main reason for this is to ensure that the data is correctly encoded into the card.

More often than not, this encoded data will often consist of important information entirely unique to your credit card account, including your account number and issue date. 

With that being said, when a credit card is then swiped, in order to successfully get charged, the credit card reader will be able to successfully take all of the information that has been encoded into the black line by cleverly reading the pattern of the magnetic and non-magnetic areas.

If there is a reason why the credit card reader is unable to successfully read this black line and gather all of the information needed to charge it to your account, then the transaction will be declined – even if you know that you have enough money in your account to make the purchase in question. 

As you might have already been able to guess, the black line that runs down the back of your credit card is very sensitive and prone to becoming damaged from a variety of different factors, including general wear and tear, scratches, and if it gets exposed to a stronger magnet that could have the potential to corrupt the encoded data and render it unreadable to a credit card reader.

Whatever the reason might be, when the black line’s carefully constructed order gets tampered with, the magnetic and non-magnetic areas can get jumbled together and mixed up, and this is something that is officially referred to as “smearing”. 

When smearing occurs, it can cause the encoded data to become distorted and, in turn, difficult for a card reader to be able to decipher.

Due to this, it means that, more often than not, the card reader will come back with a giant “error” message across its screen, rather than a “transaction approved”. Luckily, this is where plastic bags come in to save the day.

When wrapped inside a plastic bag, the jumbled parts of the black line will be muted by the bag, and this will then allow the credit card reader to read the black line successfully and put the purchase through. 

As a side note, even though plastic bags are exceptionally good at being able to help credit card readers decode corrupted credit cards, it should be kept in mind that they do not offer a 100% accuracy guarantee, which is why we recommend that you ensure to get faulty credit cards replaced with a new one as soon as you notice the issue beginning to arise.

Alongside that, if you wanted to be extra safe in the instance of an emergency, then you could also consider carrying spare cash during shopping trips, too. 


Bruce BoswellBruce Boswell

Bruce Boswell

Bruce Boswell enjoys researching and writing about all things related to investing and saving money. Whenever he has a chance, Bruce loves travelling all around the world with his wife and trying new foods.