There is inconsistent behavior between filtering on data in the Desktop version of Excel and in the web version of Excel.
In the situation where the top row of the table is a table header with 2 or more cells merged and the actual table headers on the second row with data in each column the following behavior shows.
- The top header row is skipped when more than two cells are merged, and filtering starts at the second row where the real headers are. This is the right behavior.
- When only two cells are merged for the top header then filtering starts at the top row.
- The top header is taken as the filter instead of being skipped regardless of how many cells are merged for the top row.