Cannot change column type: it is currently being indexed

Short answer: back up the list first, because changing a column type can change what is stored. Then turn off Enforce unique values on the column, delete its index on the Indexed columns page, change the type, and add the index and the unique rule back if you still want them. A Microsoft Q&A answer from April 2026, about a related type-change error, gives the same order: remove the index, make sure Enforce unique values is No, change the type, then re-enable them if needed.

What the message means

You open a column in List settings and try to change its type, for example from Number to Single line of text. SharePoint answers: "the type of this column cannot be changed because it is currently being indexed."

An index is a lookup aid. SharePoint builds it for a column so that filtered views can find rows faster. A column can have an index for two reasons:

Someone added the index on purpose, to speed up views on a big list.
Someone turned on Enforce unique values. Microsoft says a unique column needs an index, and the index is created for you when you select OK.

A column can also be blocked by something other than an index. A Microsoft Q&A answer says that when a column is involved in certain features or dependencies, "SharePoint blocks the change and returns a non-supported field type error." It names one case: a calculated column that uses the column, when you change Single line of text to Multiple lines of text. If you remove the index and the change still fails, check for calculated columns that use this column. If the error stays, the same answer says creating a new column is the supported approach, and it suggests hiding the old column instead of deleting it.

What follows combines what Microsoft documents about indexes with answers in a Microsoft Tech Community thread about the same message, plus that Q&A answer.

What Microsoft documents about indexes

Microsoft's page on adding an index says: "You can add indexes on up to 20 columns on a list or library." The same page says that to delete an index you select it on the Indexed Columns page and then select Delete.

Microsoft's page on unique columns says that a column can be required to hold unique values. It also says: "you can't remove the index from that column unless you first redefine the column to allow duplicate values." So for a unique column, the order matters. Allow duplicates first. Then delete the index.

Our advice, not a Microsoft rule: copy the list first, because a type change can change or lose what is stored. That is why Step 1 is a copy.

What a Microsoft Tech Community thread says

A person in a Microsoft Tech Community thread got this error when changing a Number column to Single line of text. The answers in the thread give the same fix, in two forms:

One answer gives four steps: turn off Enforce Unique Values, remove the column index, change the column type, then turn Enforce Unique Values back on.
Another answer says indexed columns appear on the list settings page under the Columns section, and advises: "Remove indexing on the number column & then try changing the column type."

One person in the thread reported that removing the index kept showing a wait message. The thread does not show how that ended. If that happens to you, see the section on a stuck delete below.

Step 1. Copy the list before you change anything

A type change can change or lose what is stored in a column. Do not rely on memory about which changes are safe.

Open the list.
Export it to Excel, or save a copy of the list with its data. For a way to copy, see "How to back up a SharePoint list before someone wrecks it".
Write down the column name, its current type and whether it is required.
Write down every view that filters or sorts on this column.

Our advice, not a Microsoft rule: do not start the type change on a live list that people are editing. Pick a quiet time.

Step 2. Find out why the column is indexed

Open the list.
Open the gear icon, then List settings. Exact names may differ in your version.
Under Columns, select Indexed columns.
Look for your column in the list of indexes. Write down whether it is the primary column of the index.
Go back and open the column itself. Look for Enforce unique values. Note whether it is set to Yes.

If Enforce unique values is Yes, you must turn it off before the index can go. If it is No, the index was added by hand and you can delete it directly.

Step 3. Turn off Enforce unique values

Skip this step if the setting is already No.

In List settings, select the column name.
Find Enforce unique values and choose No.
Select OK.

This is the step Microsoft's page describes as redefining the column to allow duplicate values. While it is off, the list will accept repeated values in this column. Ask people to pause edits until you finish.

Step 4. Delete the index

In List settings, select Indexed columns.
Select the index for your column.
Select Delete.
Open Indexed columns again and confirm the index is gone.

If the index covers two columns (a compound index), the column you want to change may be the primary or the secondary column. Microsoft's page says a compound index has a Lookup column as the primary column and a non-Lookup column as the secondary one. Deleting the index removes it for both columns, so note which views relied on it.

Step 5. Change the column type

In List settings, select the column name.
Change the type setting to the new type.
Select OK.
Open the list and check a few rows. Compare them with your copy from Step 1.

Check numbers, dates and blanks first. Text that looks like a number can behave differently once the type changes. If a row looks wrong, stop and restore from the copy.

Step 6. Add the index and unique rule back

Only do this if you need them.

In List settings, select Indexed columns, then Create a new index.
Pick the column as the primary column. Select Create.
If you want unique values again, open the column and set Enforce unique values to Yes. Select OK.

Check the new type first. Microsoft's index page lists column types that can't be indexed: multi-line text, multi-valued choice, calculated, hyperlink or picture, custom, multi-valued person or group, and external data columns. If your new type is on that list, you cannot add the index back. Microsoft's page also says creating an index needs to read every item, so you may be blocked from creating one if the whole list is over the List View Threshold.

If the new type is Single line of text, Choice (single value) or Number, you can try the index again. For how unique values behave, see "Stop duplicate entries in a SharePoint list".

Before you turn unique values back on, look for repeated values in the column. Ask your admin if the column already holds repeats.

If the delete seems stuck

A person in the Microsoft Tech Community thread reported a wait message that did not clear when removing the index. Our advice, not a Microsoft rule:

Close the page and open List settings again.
Check Indexed columns to see whether the index is already gone.
Check whether the list is very large. Microsoft says a list view threshold of about 5,000 items can block some operations. See "SharePoint list over 5,000 items: what breaks and the fix".
If the index is still there after a few tries, copy the list data to a new list with the right column type and move your views and flows to it.

What to avoid

Do not skip the copy. A type change can alter stored values and I cannot tell you which ones.
Do not delete the index while Enforce unique values is Yes. Microsoft says the index cannot be removed until the column allows duplicates.
Do not add indexes to every column. Microsoft's limit is 20 indexed columns on a list or library.
Do not forget the flows. A Power Automate flow that reads this column may expect the old type. Open each flow that uses the list and test it after the change.

Views that depend on the same column

If a view filters or sorts on this column, open the view after the change and check it still works. Our advice, not a Microsoft rule: write down each view's filter before you start, so you can rebuild it if the type change breaks it.

When to get help

You can build all of this yourself in Microsoft 365. If you would rather have it built and tested for your team, I do that. A tracker like this is a fixed price: $5,000 for one, built in 2 weeks. See "What a SharePoint tracker costs to build". Bring one example of the problem to a free call.

Tell me what's still manual

I am Al Davies. I run 250 High Street LLC and build SharePoint trackers and Power Automate flows for operations teams. I work remotely. The first call is free, and I will not try to sell you anything.

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FAQ

Why does SharePoint say the column is being indexed when I did not add an index?

Microsoft says a unique column needs an index, and the index is created when you select OK. If someone turned on Enforce unique values, the column has an index even if nobody opened the Indexed columns page. Microsoft's unique and lookup columns page also says: "Lists will automatically index columns in order of creation date to optimize sorting in large lists."

Can I change the type without losing data?

Our advice, not a Microsoft rule: a type change can change or lose what is stored. Copy the list first, change the type, then compare rows with the copy before you let people back in.

The index will not delete. What now?

First confirm Enforce unique values is No. Microsoft says the index cannot be removed from a unique column until it allows duplicates.

What if the type still will not change after I remove the index?

A Microsoft Q&A answer says SharePoint blocks a change when the column is tied to other features, such as a calculated column, and suggests creating a new column and hiding the old one.

How many columns can I index?

Microsoft's page says: "You can add indexes on up to 20 columns on a list or library." Some column types cannot be indexed at all.

Do I need to add the index back?

Only if you filter on this column in a big list, or you need unique values. Our advice, not a Microsoft rule: add an index only where you need it.