SDGregory, I have not been able to reproduce the phenomenon you describe. I would take a look at the actual data in the table. Has anything about the table structure ever changed that could affect the data? A different input mask, perhaps? One would think that this would have no bearing on an empty field, but perhaps somehow some records actually hold blank (i.e. non-printing) characters. You might try querying the table, and specify "Is Not Null" for the criteria for the fax number field and see what the datasheet displays. You might try an update query and search for records that have non-numeric data in the fax field, and replace with "". I don't know off the top of my head what query expression would accomplish this, just throwing out ideas. And of course, anything you try in this regard should be thoroughly tested on a backup copy of your table before you execute it on live data.
Ken S.