If your source data is in Excel and has duplicates, run Power Query to remove those duplicates before running a Word mail merge.

When working with Excel files that have different sheet names or layouts, Power Query can dynamically detect and extract the necessary data.

Microsoft Excel is perhaps the most powerful spreadsheet application you can buy. But it also has some simple functions, like finding duplicates in data.

When a conditional formatting rule is overkill, use these VBA procedures to highlight duplicates and then remove the highlighting in Microsoft Excel.