Can you enable Credit Notes or Convert Invoice to Credit Memo in QuickBooks Online Essentials so I can create 110 credit notes from invoices?

Welcome to the Community, Michailidouinsurance. There's no need to enable the Credit Note feature as it is a built-in feature available in QuickBooks Online Essentials.

You can locate it by clicking on the + Create button and navigating to the Customers column, where you'll find the Credit Note option.

Please know that invoices cannot be converted into Credit Notes or Credit Memos. However, you can use credit notes to apply it to your invoices.

Here's how to create a Credit Note: 

1. Click on + Create and choose Credit Note.
2. In the Customer dropdown, select the appropriate customer.
3. Fill in the necessary details such as date, amount, and any returned products or services.
4. If any stock needs to be added back, include it as a line item.
5. Click Save and Close to finalize.

To apply Credit notes to your invoices, here's how: 

1. Select on + Create, and select Receive payment.
2. From the Customer dropdown, select the customer.
3. In the Outstanding Transactions section, select the invoice.
4. In the Credits section, select the credit note(s) you want to apply.
5. Adjust amounts if needed, then select Save and close.

If the Automatically apply credits option is enabled in QuickBooks, credits will automatically be applied to your invoices. But if the feature is disabled, you will need to manually apply the credits. To check whether this option is activated, refer to the instructions outlined in Step 1 within this article: Create, apply, or import credit notes and delayed credits in QuickBooks.

Feel free to reply if you have any additional questions or concerns. We’re here to help.