Note: Cash on Delivery (COD) payment method fees are only available on the Plus Plan with Shopify Plus.
If you're not on Shopify Plus, you can still set up fees for credit card transactions.
To add a fee when someone pays by Cash on Delivery:
In your Shopify admin, go to Online Store > Apps and open Magical Product Fees.
Click Create fee.
Choose the Function Method.
Enter a title, like "Cash on Delivery Fee."
(Optional) Add a description.
Under Payment Methods, click Add Payment Methods.
Check Cash on Delivery (COD).
Click Save.
This will charge the fee only when Cash on Delivery (COD) is selected at checkout.