This article gives a step by step solution to stack multiple discount codes at checkout on your Shopify store
Install an app to allow multiple discount codes in Shopify
By default, Shopify allow the customer to use only one discount code at checkout at the same time. There is no options in Shopify to modify this behavior, but fortunately, Shopify also has a great app store and some apps allows to fix this problem by extending Shopify default features.
In this tutorial we will use DiscountDuck ( click here to see the app on the app store ). This app allows to create and stack as many discount codes as you want, but you can also create and stack automatic discounts if you want to.

Enable discount code input on cart page
The first step is to enable the discount code input. To be able to apply multiple discount codes, DiscountDuck add a new discount code input on cart page. This new input allows your customers to use the discount codes created from DiscountDuck and see the discounts applied live on cart page.
Click on “Configuration” and “Cart widget”

Then scroll down and click on “enable discount code input”

Now, open your cart page, the new input should appear under the subtotal.

Depending on your theme, the integration may require a few more step, please check this page if you don’t see the input at this step :
https://redcod.crunch.help/widgets-configuration/change-cart-widget-position
Create multiple discount codes
Create the first discount code
We will now create multiple discount codes, open the app from your Shopify administration panel and Click on “Create new offer”.

Select “Stackable discount code”

Fill in the form with a name for the offer and for the discount code. The discount code name will be the one you will share with your customer to apply the discount.
You can choose if you want the discount code to be stackable or not, if you check “Stackable with other offers from DiscountDuck” checkbox, this discount code will be stacked with other offers from the app. Here we will let the checkbox checked because we want to stack two discount codes.

This first offer will use the code “SUMMER10” to apply a 10% discount on all store products so we will set the discount value to “10” and choose “percentage”

Once the configuration is done, click on save at the bottom right of the page.

Our first offer is online 🎉. You can now use the discount code on the cart page. It will automatically show the discount for each product.

Create the second discount code
For the second discount code, we will repeat the same steps as for the first offer ( don’t forget to let the “Stackable” checkbox checked ). For the example, we will create a Black Friday offer giving a 30% discount on all store with the code BLACK30. This new offer will be stackable with the previous SUMMER10 discount code.

Now, let’s go back to the cart page and add this new discount code.

The two discount code are properly stacked and we now have a 10% + 30% discount applied with our two different discount codes 🍾