SharePoint Document Issues

How to Fix SharePoint API Error When Updating the Day1 Column

Olivia Miller Sep 27, 2026 869 views

Question details

The user is encountering an API error when attempting to update a SharePoint list column named Day1, indicating the property does not exist.

How to Fix SharePoint API Error When Updating the Day1 Column

Product: Microsoft SharePoint
Device & OS: not provided
Scenario: Updating list item column properties via the SharePoint REST API.
Observed behavior: The API request fails with an error stating that the _x0044_ay1 property does not exist on the list item type, even though other fields update correctly and permissions are valid.

Before you start

Ensure you have the necessary developer permissions to query list metadata and verify that your API authentication tokens are currently valid before proceeding.

Solution 1Recommended

Verify the Exact Internal Field Name and Entity Type

Use the SharePoint API to retrieve the exact metadata for your list fields to ensure you are targeting the correct internal name and entity type in your request payload.

SharePoint often applies strict encoding to column names during creation. A column named 'Day1' might be internally encoded as '_x0044_ay1' or 'OData__x0044_ay1'. You must retrieve the exact metadata properties to format your API request correctly.

Query Field Metadata

Make a GET request to the endpoint `_api/web/lists/getbytitle('YourListName')/fields` to retrieve all field definitions for your specific list.

Locate the Day1 Column

Search the JSON response for the 'Day1' column and carefully copy the exact value of the `EntityPropertyName`. This is the property name you must use in your update payload.

Verify List Item Entity Type

Send a GET request to `_api/web/lists/getbytitle('YourListName')?$select=ListItemEntityTypeFullName` to retrieve the correct entity type for your list.

Update the Request Payload

Modify your POST or PATCH request body so the `@odata.type` matches the entity type retrieved, and the property key exactly matches the `EntityPropertyName` (e.g., `OData__x0044_ay1` or `Day1`).

Encoding in SharePoint: SharePoint automatically encodes special characters and sometimes standard capitalization in internal names upon creation, which is why a standard name like 'Day1' might appear unexpectedly as '_x0044_ay1'.

Solution 2

Consult the SharePoint Developer Community

If the API continues to reject the request despite correct metadata, escalate the issue to developer forums for targeted troubleshooting.

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Frequently Asked Questions

Why does SharePoint add '_x0044_' to my column name?

SharePoint encodes certain characters in internal column names to ensure compatibility with XML and URLs. For example, a capital 'D' can be encoded as '_x0044_' depending on how the column was initially created and indexed.

How do I easily find the correct internal name of a SharePoint column?

You can find the exact internal name by navigating to your List Settings via the browser, clicking on the specific column name, and looking at the end of the URL for the 'Field=' parameter.

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