I generate invoices from scratch and also from estimates, but they look different and I don't know what setting to modify so they both look the same. Can anyone help?

Let's figure out why your invoice and estimate template are different and fix it, GuillermoR.

Before anything else, have you set your invoice design style into default mode? Additional details would help us find the exact solution to fixing your preferred template style in both invoice and estimate.

You can customize your preferred template by creating both invoices and estimates of the way it looks in QuickBooks Online (QBO).

In the meantime, to ensure that your invoices are uniform we can manually select a preferred style for creating an invoice from scratch.

Here's how:

1. Convert an Estimate to an Invoice or go to the + New button, then select Invoice.
2. Click the Manage icon.
3. Find the Design option.
4. Select your preferred template.

Additionally, you'll want to check this article for more tips on personalizing your sales forms: Customize invoices, estimates, and sales receipts in QuickBooks Online

Moreover, here's an article on managing invoice payments and turning an estimate into an invoice in QBO: 

• Record invoice payments in QuickBooks Online
• Convert an estimate into an invoice in QuickBooks Online 

If you've got more concerns about customizing the sales form or any QBO-related queries, please utilize this thread anytime. We're all here to help you.