To increase the font size of invoices in Quickbooks, you need to customize the invoice template. Here are the steps to do that:
1. Go to the Sales menu and select Invoices.
2. Click on Customize and choose Edit Current.
3. In the Design tab, click on the Fonts button.
4. Select the font size you want for each section of the invoice, such as Date, Invoice number, Customer name, etc.
5. Click on Done to save your changes and preview your invoice.
You can also create different templates for different customers or purposes, and apply them when you create or send an invoice. For more information, you can visit the Quickbooks Help Center or contact their support team.
Thanks
Paul