Returns whether the given value is an error but is not an #N/A error ("not available"). ISERR ( NA ()) ISERR ( NA ()) returns FALSE. (The NA function returns an #N/A error.) However, ISERR (Value1 / Value2) ISERR (Value1 / Value2) returns TRUE when Value2 is 0 or blank, resulting in a #DIV/0! error ("division by zero").

Lookup functions like XLOOKUP return #N/A errors when a value cannot be found. The ISNA function may be used to detect the #N/A error specifically.

This formula returns TRUE, because the sought value, 10, is not part of the { 20, 30 }{ 20; 30 } lookup array given to XLOOKUP:

ISERR is the opposite of ISNA, meaning that it detects all errors except for #N/A errors. Consider this formula:

The preceding formula returns TRUE if Value2 is 0 or blank, resulting in a #DIV/0! error, but it returns FALSE if the value resulting from the Value1 / Value2Value1 / Value2 calculation cannot be found in the lookup array.

The ERROR.TYPE function can be used to determine the precise error type.