Software⏱️ 3 min read📅 2026-06-19

How to Fix: Custom reference number too long in footnote error in MS Word

Error in MS Word footnote due to custom reference number being too long. Find a solution.

Quick Answer: Check the length of your custom reference numbers and shorten them if necessary.

📋 Table of Contents

  1. 💡 Why You Are Getting This Error
  2. ✅ Best Solutions to Fix It
  3. 💡 Conclusion

The error 'Custom reference number too long' in MS Word occurs when you attempt to add a footnote to a document, but the custom reference number exceeds the maximum allowed length. This issue affects users who are trying to create complex referencing systems or use very long citations.

This error can be frustrating, especially when working on documents that require precise referencing. However, don't worry, as we have some steps to help you resolve this issue.

💡 Why You Are Getting This Error

  • The primary reason for this error is that MS Word has a limit on the length of custom reference numbers. This limit is designed to prevent users from entering extremely long or complex numbers that could cause formatting issues or crashes.
  • Another possible cause is that you may have accidentally entered a special character or symbol in your custom reference number, which can exceed the allowed length.

✅ Best Solutions to Fix It

Extend the maximum allowed length for custom reference numbers

  1. Step 1: Open your document and go to the References tab.
  2. Step 2: Click on the 'Footnotes' group and select 'Settings'.
  3. Step 3: In the Footnote Settings window, click on the 'Custom' button next to 'Reference Label'.
  4. Step 4: In the Custom Reference Label dialog box, click on the 'Edit' button.
  5. Step 5: In the Edit Custom Reference dialog box, you can adjust the length of the custom reference number by entering a new maximum value. The default maximum length is 255 characters, but you can increase this limit if needed.
  6. Step 6: Click 'OK' to save your changes and try adding the footnote again.

Use an alternative referencing system

  1. Step 1: If extending the maximum allowed length for custom reference numbers is not feasible, you can consider using an alternative referencing system.
  2. Step 2: One option is to use a superscript number instead of a custom reference number. To do this, select the footnote text and go to the 'Home' tab.
  3. Step 3: Click on the 'Superscript' button in the 'Paragraph' group.
  4. Step 4: This will convert the selected text to superscript format, which can be used as an alternative to custom reference numbers.

💡 Conclusion

By following these steps, you should be able to resolve the 'Custom reference number too long' error in MS Word and successfully add footnotes to your document. If you continue to experience issues, consider reaching out to Microsoft support for further assistance.

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