When you file is that large, you might want to consider condensing old data if you have no need to access it often. You will be forced to create a back-up copy before condensing.
I do not use the QB file transfer, nor do I want my clients to send me back-ups or accountant's copies. You need a file transfer service that your account also has. I use Remote Accounting Service. Have been using this for 15 years without issues. All of my clients transfer files this way and the cost is $15 month per user if used and zero if no transfers occur. There is a set-up cost that your accountant will have to pay to initiate the service.
