It seems that accounting packages are better at importing data than they are at exporting data in a generally usable form. Which is unfortunate since I use QuickBooks and my accountant uses SAGE.
To make life easier for my accountant when doing my annual return, I wrote some Perl scripts to convert the little that QuickBooks exports as files plus, via Excel, the data from a non-standard transaction report into what SAGE imports. The account balances on the two packages now all match (though at one point yesterday, account balances in one were -2 times the balances in the other).
I am expecting that the accountant will find few enough things to correct that I won’t have to automate conversion in the other direction.