Hi there, @MLImn.
I'll share some insights on how you can get the monthly historical balances as you merge the company records into one complete file.
You can load the general ledger balances for prior periods en mass. Make sure to check the date for it will matter for the detail of your report. When you plan to open a monthly reporting, then you can fasten it to monthly. If quarterly, then you can set it to quarterly.
You can go to the File menu and then select Utilities. Choose Import and then pick General Journal Entries.
Also, you may need to have a reference if you're going to import general ledger balances from a different program, you can check this article: IIF Overview: import kit, sample files, and headers. The general ledger balances must have to be an IIF (Intuit Interchange Format) file to save it in QuickBooks.
Additionally, you may want to use journal entries to adjust your clients' books and make a few minor corrections.
Let me know if you have some questions. I'm always here to lend you a hand. Stay safe and well,
