I am using Reckon Accounts Personal Plus 2013. I have attached an incorrect file to a transaction. When I try to delete the attachment, I get the following message: "The process cannot access the file because it is being used by another process".
Had the same issue. When you are "looking" at the attachment, if its a pdf file, then Adobe Reader (or equivalent) is operating in the background (which is the "another process"). Hence the error message. So you have to shut this programme down. To do this, hit CTRL + ALT + DEL and open Task Manager. In the list of programmes, you know need to find the programme that is reading the pdf file, and close it. When you go back to your Reckon programme you won't be able to read the attached document any longer (which is fine). Just hit "Delete" at the bottom of the screen, and it should be done. [Apologies if you can't follow my instructions]