I'll guide you on adding your financing link in the Website field or Message to customer on or in the Add Footer text for your estimates, invoices, and sales receipts in QuickBooks Online (QBO), Christinamnc.

Here's how to do it:

1. Go to the Gear icon.
2. Select Custom form styles.
3. Find your template and click Edit under the Action column.
4. Go to the Content tab and click the header part of the invoice. Add your financing link under the Website field or go to the footer area and add the information in the Add footer text or Message to customer field.
   
   
   
   
5. Go to the Emails tab and enter your website and social URLs in the Message to customer field. Please know that the link you want to add in the boxes will be converted into texts.
   
   

    

6. Click Done. 
   

To learn more about adding specific information to your sales forms, please refer to this article: Customize invoices, estimates, and sales receipts in QuickBooks Online.

In addition, you can check this article to learn how to automatically or manually send reminders to customers when your invoices are, or soon to be, overdue: Send invoice reminders automatically or manually in QuickBooks Online.

Let me know in the comment section if you have other concerns about customizing your sales forms in QBO. We're always here to help.