Hi,

A couple of comments.

First off it takes a bit of mental shift to switch from thinking in terms of file and folders to thinking in terms of SQL Server databases.

I would not design a system around one database per customer per year. At the most I would consider one SQL database per customer or even one large database designed to handle all customers / all years.

I would not try and move databases between the customer and the accountant. Depending on the availability of an Internet connection between the accountant and the customer, you could leave the data at the accountant's site. A well designed app can run just fine over any reasonable Internet connection. I had a case once where we had an application running against a SQL Server which was installed on the LAN. The SQL Server was a slower older box, but application performance was still acceptable. Later we moved the SQL Server to a new faster box located about 4000 km away and accessed it via the Internet. The application actually ran faster on the new faster server even though the new server was not on the LAN. You can also look at setting up a VPN tunnel between the sites to enhance security.

Best regards,

Tim