Let me provide additional information about attachments in QuickBooks, ShopAdmin.

Attachments can't be attached directly to list items, such as Accounts or Employee Names. Attachments can't contain special characters in the file name. Adding an attachment to customer or vendor profiles and their transactions helps organized the records. The security message you received when attaching documents will usually prompt when the file type you're trying to attach is other than the following supported file types. Also, make sure that you're using the accepted characters and file types to avoid any errors.

In addition, take note these are the only file types you can attach in order to protect the security of your account:

• PDF
• JPEG
• PNG
• DOC
• XLSX
• CSV
• TIFF
• GIF
• XML

If the file is already saved as one of the listed supported file types, try removing the extra space between the file and the extension. The file name should look like this "filename.pdf", then add the attachment once more.

If the same issue after checking the requirements of attachments You may be experiencing some browser hiccups. We'll perform the basic troubleshooting to fix this. Let me guide you.

We'll start with logging into your account through a private browser. It's the best place to identify web issues. These are the shortcut keys:

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

If you can add the attachment successfully using the private browsing session, go back to your regular browser and clear its cache to refresh the program.

To learn more about how attachments work in QBO through this article: Attachments in QuickBooks Online.

The Community is always open whenever you need help with QuickBooks. Stay safe and have a nice day ahead!