Hi, @nctriangle.

You should be able to add an attachment to your invoices from the Attachments section. If not, I recommend adding up the file using a private window. In most cases, unexpected behavior while working with QuickBooks is caused by too much cache stock on the regular browser you're using.

To save you time, use either of these keyboard shortcuts:

• Google Chrome: Ctrl + Shift + N
• Safari 11 or newer: ⌘ + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Microsoft Edge: Ctrl + Shift + P

If it works, I recommend going back to your original browser, then clear its cache to start fresh. You can also use other supported browsers and have added Intuit as a trusted site to prevent your browser from potentially blocking site content.

On the other hand, here's how you can add attachments to your customer and vendor profiles, as well as their transactions.

For more hints while working with QuickBooks Online, you can also open the topics from this link: Find QB help articles, video tutorials, and more.

Please keep me posted if you have any other questions about adding attachments to your customer's invoices. I'm always here to help. Have a good one!