In Excel, which error value indicates that a formula is referring to a cell that is not valid?

The value #REF! indicates that a formula is referencing a cell that is no longer valid. This error typically occurs when a cell that a formula points to has been deleted or if the formula references an invalid range. For example, if a user creates a formula that includes the cell reference A1, and then later deletes that cell, the formula will return a #REF! error, signifying that it cannot find that reference.

This error is essential for users to address because it highlights issues in data integrity and formula accuracy. By resolving #REF! errors, users can ensure that their calculations reflect the correct data and maintain the functionality of their spreadsheets.