How to Fix Invalid Assignee ID in Power Automate SharePoint Task Flow
Question details
The user needs to resolve an error occurring in a Power Automate flow when attempting to assign a task to multiple users pulled from a SharePoint list.
- Product
- Power Automate / SharePoint
- Device & OS
- not provided
- Scenario
- Creating a task in Power Automate using assignee data retrieved from a multiple-selection SharePoint Person column.
- Observed behavior
- The flow rejects the SharePoint Person column data and throws an 'Invalid Assignee ID' error because the action expects a specific format for assigned users instead of an array object.
Ensure you have edit permissions for the Power Automate flow and the corresponding SharePoint list. Verify that the SharePoint Person column is configured to allow multiple selections.
Format Multi-Person Column Emails using Select and Replace Actions
Extract the email addresses from the multi-person column and format them into a semicolon-separated string using a Select action and a replace expression.
Task actions in Power Automate (such as Planner or standard Create a Task) strictly require assigned user emails or IDs to be formatted as a flat, semicolon-separated string. Because SharePoint multi-selection Person columns output an array of complex metadata objects, passing this directly will trigger the Invalid Assignee ID error.
Add a 'Select' action to your flow. In the 'From' field, select the dynamic content of your multiple-selection SharePoint Person column. Map the output to extract only the 'Email' values.
Use an expression to clean the array and format it into a semicolon-separated string. For example, add a Compose action and use the expression: replace(replace(replace(join(body('Select_2'),','),'{"Email":"',''),'"}',''),',',';') (ensure you adjust 'Select_2' to match your actual Select action name).
Insert the output of your Compose action (the clean, semicolon-separated addresses) into the 'Assigned To' field of your 'Create a Task' action.
Save your Power Automate flow and trigger a test run. Verify that the task is created successfully without the Invalid Assignee ID error.
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Frequently Asked Questions
Why does the 'Invalid Assignee ID' error occur in Power Automate?
This error occurs because task creation actions expect a flat, semicolon-separated string of email addresses or user IDs. When you provide data directly from a multiple-selection SharePoint Person column, you are passing an array of complex JSON objects, which the action cannot parse as valid assignee IDs.
Can I use user object IDs instead of email addresses to assign tasks?
Yes, depending on the specific task action (such as creating tasks in Planner), you can use Microsoft Entra ID (Azure AD) Object IDs. These IDs must also be formatted correctly and separated by semicolons if there are multiple assignees.
How do I check the output of my Select action before creating the task?
You can add a 'Compose' action immediately after your formatting expression in the flow. Run a manual test flow and review the output of the Compose action in the run history to ensure it returns clean, semicolon-separated email addresses without any residual brackets or quotes.
