Hello there, @LillanLillan.
The option to customize the font size of balance due on invoices in QuickBooks Online is unavailable. Alternatively, you can export it to Excel, so you'll have the freedom to personalize the appearance of your invoices according to your preferences.
Don't worry. We listen to customer feedback to improve your QBO experience. I am here to help you share your valuable insights with our software engineers. This way, they will review your suggestion and possibly consider it for our next product enhancements.
Here's how:
- Go to the Gear icon.
- Under Profile, select Feedback.
- Enter your feature request, then Next.
Moreover, once you've created an invoice for your customer, you can send it via email. Please check this article as a guide: How to Email an Invoice in QuickBooks Online.
We will ensure a prompt response if you have any other concerns with your invoices. Please keep us updated.