Hi @BogDog33,
The error doesn't directly relate to the validation formula itself, but indicates that there could be an issue with data submission when the validation condition is not met.
You can try to use these steps to resolve your issue:
1. Make sure the validation formula you entered ('=EndDate>StartDate') is correct and doesn't have any mistakes. Check if the column names match exactly with those in your SharePoint list.
2. Test the Validation Condition: try to create a new item in the list and intentionally enter an EndDate that is not greater than the StartDate. So you can see if the validation works as expected and prevents the item from being added.
3. Double check the 'User Message' you specified in the Validation Settings. It should be written and without any characters or elements that might cause conflicts or issues.
5. Test in Different Environment: try testing the same validation formula in a different SharePoint environment, like a test site or. This can help determine if the issue is specific to your current environment (site)
Start and End dates validations in Sharepoint list - Microsoft Community
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Kindest regards,
Leon Pavesic
