Can ISOMITTED tell if a cell is empty?

No. ISOMITTED only reports whether a LAMBDA argument was omitted when the function was called. To test for empty cells, use ISBLANK or LEN=0.

Why does ISOMITTED return #VALUE! in my formula?

Because the function is being evaluated outside a LAMBDA. ISOMITTED needs the context of a custom function call to know if an argument was left out. Wrap the logic inside a LAMBDA and the error disappears.

Can I use ISOMITTED with multiple optional arguments?

Yes. Inside a LAMBDA you can call ISOMITTED for each parameter individually and branch accordingly, allowing you to supply defaults for any number of optional inputs.

Is ISOMITTED available in Google Sheets?

No. ISOMITTED is an Excel-only function introduced in Office 365. Google Sheets users must rely on alternative patterns, such as checking for the special error value NA() or using IFERROR.

ISOMITTED function

ISOMITTED returns TRUE when a LAMBDA argument was left out, otherwise FALSE, letting you supply defaults for optional parameters in Excel 365.

=ISOMITTED(argument)

Generate a ISOMITTED formula

Describe what you need. The generator will reach for ISOMITTED where ISOMITTED is the right tool, and tell you when it is not.

Arguments

How ISOMITTED reads its arguments

Argument	Required	Description
argument	Required	The argument to test; can be any type, but ISOMITTED only works inside a LAMBDA – omitted arguments evaluate to TRUE, supplied ones to FALSE.

Returns

A Boolean TRUE/FALSE value returned as a single cell result.

Availability

Excel: 365 · Google Sheets: Not available

Worked examples

1. Calculate percentage with optional max score

Student	Subject	Assignment	Score	Max Score
Alice	Math	HW1	85	100
Bob	Math	HW1	78	100
Alice	History	Essay1	90	100
Bob	History	Essay1	85	100
Charlie	Math	HW1	92	100

=LET(
  pctLambda, LAMBDA(score, maxScore,
    IF(ISOMITTED(maxScore), score/100, score/maxScore)
  ),
  pctLambda(85, )
)

Result: 0.85

The LET creates a LAMBDA named pctLambda that expects a score and an optional maxScore. In the call pctLambda(85, ) the second argument is omitted, so ISOMITTED returns TRUE and the IF branch divides 85 by the default 100, yielding 0.85. If a maxScore had been supplied, the division would use that value instead.

2. Optional subject filter for a grade lookup

Student	Subject	Assignment	Score	Max Score
Alice	Math	HW1	85	100
Bob	Math	HW1	78	100
Alice	History	Essay1	90	100
Bob	History	Essay1	85	100
Charlie	Math	HW1	92	100

=LET(
  filterLambda, LAMBDA(subject,
    IF(ISOMITTED(subject),
      FILTER(A2:E6, (A2:A6="Alice")),
      FILTER(A2:E6, (A2:A6="Alice")*(B2:B6=subject))
    )
  ),
  filterLambda("Math")
)

Result: AliceMathHW185100

The LAMBDA filterLambda takes an optional subject argument. When called with "Math", the argument is supplied, so ISOMITTED returns FALSE and the FILTER includes the subject condition, returning only Alice's Math rows. If the call were filterLambda() with no argument, ISOMITTED would be TRUE and the FILTER would ignore the subject, returning all of Alice's records regardless of subject.

3. Personalised message when student name omitted

Student	Subject	Assignment	Score	Max Score
Alice	Math	HW1	85	100
Bob	Math	HW1	78	100
Alice	History	Essay1	90	100
Bob	History	Essay1	85	100
Charlie	Math	HW1	92	100

=LET(
  msgLambda, LAMBDA(student,
    IF(ISOMITTED(student), "Student name missing", "Report for " & student)
  ),
  msgLambda()
)

Result: Student name missing

msgLambda is defined to accept a student name, but the call msgLambda() provides no argument, making the parameter omitted. ISOMITTED therefore returns TRUE, causing the IF to choose the error-message branch. If a name such as "Bob" were supplied, the function would concatenate "Report for Bob" instead.

Common errors

Which ISOMITTED error are you seeing?

Error	Why it happens	How to fix it
#VALUE!	ISOMITTED was used outside a LAMBDA context, where it cannot determine omission.	Wrap the call inside a LAMBDA (or a LET that defines a LAMBDA) so the function can evaluate omission.
#N/A	The argument supplied to ISOMITTED references a cell that contains a #N/A error, propagating the error before ISOMITTED can test it.	Clean or replace the #N/A value (e.g., with IFERROR) before passing it to ISOMITTED.
#SPILL!	ISOMITTED is used inside an array-returning LAMBDA that attempts to spill results into a range already occupied.	Ensure the destination range is empty or wrap the LAMBDA call in a function like @ to force a single-cell result.

Tips and when to use something else

Use ISOMITTED only inside LAMBDA-based custom functions; it has no effect in regular worksheet formulas.
Combine ISOMITTED with IF or SWITCH to provide default values for optional parameters.
When you need to test for a truly blank cell (not an omitted argument), use ISBLANK instead.
If you require more than two optional arguments, chain multiple ISOMITTED checks inside the same LAMBDA.

Related functions

IFThe IF function returns one value if a condition is true and another (or nothing) if it is false, letting you branch logic in a cell.LAMBDALAMBDA lets you create custom, reusable functions directly in a cell, returning any value or array based on supplied parameters.LETLET lets you name a single intermediate result inside a formula, then return that result, making complex calculations clearer and easier to read.MAPMAP applies a custom LAMBDA to each element of a range, returning a new array of the same shape with the calculated results.XLOOKUPXLOOKUP returns the value from a specified return array that corresponds to a given lookup value, with optional handling for missing matches and search direction.

Frequently asked questions

Can ISOMITTED tell if a cell is empty?: No. ISOMITTED only reports whether a LAMBDA argument was omitted when the function was called. To test for empty cells, use ISBLANK or LEN=0.
Why does ISOMITTED return #VALUE! in my formula?: Because the function is being evaluated outside a LAMBDA. ISOMITTED needs the context of a custom function call to know if an argument was left out. Wrap the logic inside a LAMBDA and the error disappears.
Can I use ISOMITTED with multiple optional arguments?: Yes. Inside a LAMBDA you can call ISOMITTED for each parameter individually and branch accordingly, allowing you to supply defaults for any number of optional inputs.
Is ISOMITTED available in Google Sheets?: No. ISOMITTED is an Excel-only function introduced in Office 365. Google Sheets users must rely on alternative patterns, such as checking for the special error value NA() or using IFERROR.

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Reviewed 2026-09-17