That's because this is a 'conditional' (AKA 'cascading' or 'dependent') combobox/listbox using an alias value. When filtered, alias values are not available for display. A known issue and topic of many discussions. Cannot prevent, just work around. One way is to include lookup table in form RecordSource, bind textbox to lookup table field (set as Locked Yes and TabStop No) and set textbox next to or on top of combobox.