• The Balance Sheet and Income Statement being compared are for the same month and year.
• No account qualifier is being used in selecting the reports.
• The accounts aren't out of balance. Check this by running a Summary Trial Balance report. Any out of balance condition will be noted at the bottom of this report.

Your situation has a few other variables, though. I'd look at the owner distributions and any other equity account transactions in tracking down the difference you're looking for.