As a QuickBooks user for over five years, I can safely confirm that steps written below are evidently useful to merge QuickBooks company files.
Open QuickBooks and select Reports menu.
Choose Combine Reports from Multiple Companies and click on Add Files.
Go to another data file and click on Open.
Under the Select Reports for combining, pick out the reports you want to merge and enter the date range.
Select a report basis and click n Combine reports in Excel.
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