Office 2021 support ended on 13 October: your Excel still works, but newer formulas show #NAME?

What does Office 2021 end of support actually mean?

It helps to look at how software licensing works here. When you buy a standalone copy of Office instead of paying a monthly subscription, Microsoft commits to providing software updates for a specific period of time. That period is what Microsoft calls support, and for Office 2021, that commitment ended on 13 October 2026.

On Microsoft’s official page, End of support for Office 2021, they detail what comes to an end: direct technical help, bug fixes, and security patches for any vulnerabilities discovered after this date. They also state clearly that there are no extensions or extended security updates available. This is different from how Microsoft handles Windows, where business users can sometimes pay to get patches for a few extra years.

The lack of security patches is a serious concern for Excel because people send spreadsheets back and forth over email every day. Opening a file sent from someone outside your organization is a common way for malicious code to enter your computer, and any newly discovered security flaws in Excel 2021 will stay unpatched forever. The risk is lower if you only open files that you created yourself on your own PC, but that risk grows as time goes on.

How do I check if my Excel is 2021, 2024 or Microsoft 365?

A lot of people do not know which exact version of Excel is on their computer, especially if the computer came from an employer or a retail shop. You can check your version in about ten seconds, and knowing this helps you decide which path to take.

1. 01
   Open any workbook in Excel

   A blank one is fine.
2. 02
   Go to File, then Account

   On a Mac, open the Excel menu and choose About Excel instead.
3. 03
   Read the name under Product Information

   If it says Microsoft 365, you are on the subscription and this article only matters for files you send to others. If it says 2021 anywhere in the name, including LTSC 2021, this is your version.
4. 04
   Note the version for anyone you share files with

   The question that matters is not only which Excel you have, but which Excel the other person opening your file has.

Why does a file from a Microsoft 365 user show #NAME? in Excel 2021?

Excel for Microsoft 365 gets new calculation functions added to it every few months as part of its regular updates. Standalone versions only include the functions that existed on the day the software was released, and they never get new ones. Because of this, a subscriber using Microsoft 365 can write a formula using a function that Excel 2021 does not recognize at all.

When someone uses a newer function, Excel saves it inside the file structure with a special prefix attached to it. Every .xlsx file is essentially a compressed folder containing XML code, and when I inspected my own test files, I saw REGEXEXTRACT saved as _xlfn.REGEXEXTRACT and TRIMRANGE saved as _xlfn.TRIMRANGE. I explained the details of both in why the Excel REGEX functions return text and how TRIMRANGE stops a formula missing new rows. That _xlfn prefix is simply the tag for a function that older versions may not know.

In Microsoft’s official documentation for formula compatibility issues in Excel, they explain what happens when you open these files. If a formula relies on a function that is missing from your older version of Excel, it will display a #NAME? error instead of showing the calculated result when the spreadsheet recalculates. Their documentation shows an example with the internal prefix visible, written as =_xlfn.IFERROR(1,2).

This creates real practical problems when you are trying to work. For example, a colleague might enter =TEXTSPLIT(A2,",") to split a list of names across multiple columns, and the results fill out clean and organized on their screen. When you open that file in Excel 2021, that cell displays a #NAME? error, and any other formula, sum, or lookup that relies on that cell will fail as well, causing errors to cascade across your whole workbook.

Which Excel formulas work in 2021, 2024 and Microsoft 365?

This specific formula issue is rarely mentioned in end-of-support announcements, yet it is the main detail that dictates which upgrade option you should pick. On the Microsoft Support site, every formula documentation page features an “Applies to” section that specifies supported software versions. I reviewed those compatibility lists for the functions most frequently found in shared workbooks, and I gathered the findings into the summary table below.

The good news is that the major features introduced in Excel 2021, such as XLOOKUP and dynamic array formulas like FILTER, remain fully functional. If your shared workbooks rely primarily on those features, Excel 2021 will continue to calculate them without any issues.

Excel 2024 brings a solid selection of newer features to the table. According to Microsoft’s What’s new in Excel 2024 for Windows and Mac documentation, it includes 14 new text and array functions, and it names LAMBDA and IMAGE separately. Those 14 additions are TEXTSPLIT, TEXTBEFORE, TEXTAFTER, VSTACK, HSTACK, TOROW, TOCOL, WRAPROWS, WRAPCOLS, TAKE, DROP, EXPAND, CHOOSEROWS, and CHOOSECOLS, which are the main tools people use to break apart, combine, and restructure data.

However, Excel 2024 remains a static release with a set feature list, while the newest functions are listed for Microsoft 365 only. Powerful functions like GROUPBY, which generates summary tables directly from a formula without needing a PivotTable, as well as the REGEX functions and TRIMRANGE, will still trigger #NAME? errors in Excel 2024 just like they do in 2021. This list of incompatible functions will grow over time because Microsoft 365 continuously receives new features, while standalone releases remain fixed with whatever features they had at launch.

It is also worth noting that compatibility issues can work in the other direction as well. Even if you subscribe to Microsoft 365, a function can occasionally be retired or removed, as happened with COPILOT function stopped being available on 14 September 2026, so relying on a subscription does not guarantee that every formula you write will work indefinitely.

Should I move to Office 2024 or Microsoft 365?

You essentially have two choices here, and checking the formula compatibility table above is the simplest way to decide between them. On Microsoft’s end-of-support guidance page, they recommend that home users upgrade to a Microsoft 365 subscription. The alternative choice is to buy a standalone copy of Office 2024, following the same single-purchase model as Office 2021.

Microsoft’s official schedule on Office 2024 lifecycle page lists the retirement date for Office 2024 as 10 October 2029. Buying it gives you roughly three years of support before you face this exact same situation again, with an even wider gap in formula compatibility.

My opinion on this choice is straightforward. If you only create spreadsheets for your own personal use or internal tracking, Office 2024 is completely fine and will serve your needs well. But if your daily work involves opening files sent by clients, co-workers, or accounting teams who use Microsoft 365, you will run into broken formulas repeatedly, and a Microsoft 365 subscription is the only version that keeps up with them.

I am not listing specific prices here because software costs vary depending on your country, currency, and licensing plan. You should verify current pricing directly on Microsoft’s official store page before deciding which option to purchase.

What can I do with a #NAME? file before I upgrade?

You might not be able to upgrade your software immediately, but you still need to open and read a file sent to you today. There are three practical methods to work around this, and the right choice depends on whether you just need to see the calculated values or if you need the actual formulas to remain active.

1. 01
   Ask the sender for a values copy

   The person on Microsoft 365 can copy the columns with newer formulas and paste them back as values before sending. You get the results, and nothing needs a function your Excel lacks.
2. 02
   Ask them to use a function both of you have

   Microsoft's compatibility page says new functions can be replaced with ones available in earlier versions. A summary built with GROUPBY can often be rebuilt as a PivotTable, and a lookup or a filtered list with XLOOKUP and FILTER, which Excel 2021 has.
3. 03
   Check the totals you do get

   A total that includes a #NAME? cell shows #NAME? too, which is easy to spot. The quiet danger is a sheet where formulas are wrapped in IFERROR, because then the error turns into a blank or a zero and the report looks finished.

If you are the one using Microsoft 365 and sending workbooks out to other people, the same logic applies in reverse. Before sending a spreadsheet to a client, check what version of Excel they are running. Converting dynamic formulas to static values by copying and pasting values is the fastest fix when sending files to external users, and I regularly do this with REGEX functions before emailing files off my own PC.

This becomes even more important if you rely on artificial intelligence tools to build your formulas. Services like ChatGPT and Copilot will suggest modern functions like TEXTSPLIT or GROUPBY because they are efficient, but these tools do not know if your recipient is running Excel 2021. I wrote a guide in how to ask AI for an Excel formula and then check it on how to prompt AI tools for backward-compatible formulas, and I covered methods for verifying calculation accuracy in how to check if ChatGPT or Copilot got your Excel numbers right.