If your business falls into E-invoicing guidelines, you will be required to generate E-invoices for Credit Notes and Debit Notes as well. The process is identical to the one you follow for creating E-invoices on Refrens.
Let's see how you can generate E-invoices for Credit Notes. you can follow the same process for Debit Notes as well:
Step 1: Click on the "Generate E-invoice" button
Once you have created a Credit Note, click on the "Generate E-invoice" button on the Credit Note preview page:
Step 2: Add GSP Username & Password
Add your GSTIN, GSP(by Clayfin/Vay Network) User Name, and Password, and Click on "SAVE".
In case you are generating an IRN for the first time on Refrens, you will first have to create your GSP (by Clayfin/Vay Network) User name and Password on the e-invoice portal. For details, check out this help article.
Pro Tip: Click on "save credentials" so you don't have to do this manually every time!
Step 3: Verify details & Generate E-invoice
Once the details are verified and confirmed, click on "Generate E-invoice":
Step 4: That's it! Your Credit Note E-invoice is ready to go!
The IRN with the QR code will automatically reflect on your credit note as shown below. 
Step 5: Download the E-invoice PDF
Go to your Credit Note Preview Page > More > Download E-invoice PDF:
If you still have questions, feel free to contact us at care@refrens.com OR drop a message on live chat support for quick assistance!
Additional Resources:
How to Generate E-invoices through Refrens? (India)
How to generate E-invoices for SEZ and Export? (India)
How to pass payment details to E-invoices? (India)
How to Create GSP User Name and Password to Generate E-Invoices on Refrens? (India)
How to show IRN in a single line in documents? (India)
How to view e-invoice acknowledgment no. & date? (India)
How to enable signed QR codes in IRN generated documents? (India)
How to fetch & update E-invoice status of the invoices generated/canceled outside of Refrens? (India)
How to cancel an E-invoice? (India)