I saw discusions from other people that also had difficulty adding an attachment to a transaction in an investment account. This could be the result of INCORRECT INSTRUTIONS in Quicken. At least that was my problem. The "Account Attachments" popup says I need to click on the paperclip icon on the transaction, just like a non-investment account. This is incorrect. I eventually noticed that there was an ATTACH button in the lower right area of the transation ("Enter Edit Delete Attach"). This worked correctly. The paperclip icon is not present on transations in the investment account until the is an attachment.