Nick here from Shopify.
Refunds for stores are something which are handled natively within Shopify in the store admin. The main difference in refunds from store to store would generally be the return policy created which would be unique and different for each. Shopify has a helpful guide going through everything you need to know about refunds and how to apply them from the link here.
There are some apps in the Shopify App Store however which could be what you're looking for regarding returns. Shopify also has a guide for refunds which you can see here. Do you think this is what you could be looking for? I will link some of the most popular return apps below just in case, but it is worth looking into doing natively if you can to help save a potential monthly cost.
Hopefully, this helps and points you in the right direction for the next best steps.
All the best, Nick
If you are looking for reporting on refunds, Report Pundit can report the refunded amount, refunded quantity, products refunded with the refund date.
You can also identify which product is most refunded. You can also breakdown the refund into shipping refund, product refund, refund discrepancy, refunded taxes. Many merchants and their accountants use our refund reports to get each detail behind the total refund.
Also, I'd check this app for when you get returns that can't sold as brand new.
Post it in less then one minute, you can easily take photos of the damage or issue using the shopify app on your phone, and describe the issue.
It's super easy way to get rid of the open box returns.
You can follow the app suggested by @Nick For refund request.
For the notification related to refund, i would suggest to try WhatsApp notification app
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So this app offers one-click automation, you set it up once and it will automatically synchronize tracking between your Shopify store and your PayPal account.
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Our app will automate the return process for your Shopify store. Allow customers to submit product return request without contacting customer service.