The data that shows on the History tab in Account Inquiry and Account Maintenance is pulling from the GL_PeriodPostingHistory.m4t file (located in the ..\MAS90\MAS_xxx\GLxxx folder (xxx=company code)

Thanks! Just what I needed!

To add to the answer, the GL_PeriodPostingHistory table is kind of goofy. It only calculates the beginning balance in January. It also only writes a record if there is any activity for the account. For instance, if I have an account string that had activity in June and August of 2014, there will only be three lines for that account in 2014; one for 201401, 201406, and 201408. All other software that I've seen writes a record for each period regardless of activity and records a beginning and ending balance each period.

I found this out while writing an integration to our budgeting and forecasting software that required an entry for each period, even if it was zero dollars. It isn't too big of a deal to do that and calculate your own beginning balances, but not the end of the world. I suspect they did this to save disk space at the time.