Help is here @Construct SB.

Let's fix your invoice so you can attach receipts.

Before anything else, I'd like to learn more about your goal in attaching a receipt to your invoice.

If you mean the transaction link to the invoice about the "no more box on the side of the screen", you can look for it by clicking the Manage icon, and tapping the Suggestion tab inside the invoice form.

All linked transactions are in there. Click the Add icon to attach the transaction to the invoice.

If you mean the Attachments tab, you can look for it below the invoice form.

If nothing shows let's perform some troubleshooting steps to fix this. Begin with, signing in to a QuickBooks Online (QBO) test account and create an invoice there, then link a transaction. Click this link to route you there: https://qbo.intuit.com/redir/testdrive

If this works, then let's try to log in to your account via a private window to determine if it's a browser-related concern.

Check out these shortcut keys: 

• Google Chrome: press Ctrl + Shift + N
• Mozilla Firefox: press Ctrl + Shift + P
• Microsoft Edge: press Ctrl + Shift + N
• Safari: press Command + Shift + N

After that, create an invoice and attach a receipt there. If this works well, clear the cache of your regular browser to eliminate piled-up data. If the issue persists, you can use another supported browser or device. It might be that the current one you're using has a temporary issue with the program.

Additionally, I'll share this article to guide you on how to show the summary of customer transactions: Create and send customer statements in QuickBooks Online.

Let us know if you have additional questions about managing your invoice transaction by replying to this post. Keep safe always.