A completion report may ask for every record lacking a reference code. In Access, a text field that looks blank can contain Null or a zero-length string. A query that checks only one category can therefore miss records without the visible information the report expects.

Use a copied SELECT query and establish what missing means for this particular field. Null may mean no value has been supplied; an intentionally empty string may have been used for a different reason. Confirm the database's convention before replacing either one.

Compare the criteria on known records

In desktop Access Design View, add the relevant text field to the grid and inspect its Criteria row. Microsoft documents Is Null for missing values, a pair of double quotes for zero-length text, and the following combined criterion for either:

"" Or Is Null

Create or identify a small, non-sensitive sample with one confirmed Null, one confirmed empty string and one ordinary code. Run the separate criteria first, then the combined criterion. Keep each record's identifier visible so you can account for which category it enters.

Do not treat a numeric zero as absent simply because the report uses the word empty. Likewise, a field containing spaces has characters even if they are hard to see. Those cases need their own data-quality decision, not an assumption that the missing-value query covers them.

Preserve the distinction until the meaning is settled

If the completion workflow treats both categories alike, the combined selection can provide a follow-up list. If one category means “not applicable”, keep that decision visible so the list does not ask somebody to invent an irrelevant reference.

Inspect several returned records against the source and one expected complete record that should remain excluded. A broad blank check can still target the wrong field or the wrong reporting period.

Save the selection rule with the report, and distinguish finding records from changing them. This inspection does not require an update query or bulk replacement of existing values. Correct the collection process when the two states have been used inconsistently, then recheck the same known examples before relying on the next completion count.

Sources: Microsoft: Access query criteria.