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How to Fix Power Automate addDays and Planner Due Date Errors

Guest Writer Sep 28, 2026 869 views

Question details

The user needs to prevent Power Automate from incorrectly setting a Planner task's due date to its start date when the input due-date value is null or invalid.

How to Fix Power Automate addDays and Planner Due Date Errors

Product: Power Automate
Device & OS: not provided
Scenario: Creating or updating a Planner task using Power Automate flows that involve dynamic date calculations.
Observed behavior: The due date defaults to the start date or today's date because the provided due date field evaluates to null, empty, or an invalid parameter during the addDays or coalesce expression.

Before you start

Review your most recent failed flow run outputs to identify exactly which date fields are returning null or empty values before they reach the Planner action.

Solution 1Recommended

Validate Date Fields Using Conditions Before Task Creation

Stop the flow or handle empty values gracefully before passing null data into the Planner action.

By verifying that your start and due dates actually contain data before creating the task, you prevent the system from substituting unintended fallback values.

Open the Flow Editor

Edit your Power Automate flow and locate the step immediately before the 'Create a task' (Planner) action.

Add a Condition Control

Insert a 'Condition' action. Set the left operand to your due-date dynamic content, select 'is not equal to', and leave the right side blank (or use the empty() expression).

Configure the If/Yes Branch

Move your 'Create a task' Planner action into the 'If yes' branch so it only executes when a valid date is confirmed.

Apply addDays Function

Inside the Planner action, apply your addDays() expression directly to the validated due-date field without relying on a fallback.

Tip: Checking for null values beforehand prevents flow failures and keeps your project timelines accurate.

Solution 2

Modify the Coalesce Expression to Avoid utcNow()

Prevent Power Automate from automatically inserting today's date when the intended due date is missing.

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Frequently Asked Questions

Why does my Planner task due date show as today's date instead of the future date?

This usually happens when the due-date parameter passed to Power Automate evaluates to null, and a function like coalesce() automatically falls back to utcNow(), defaulting the task to today.

How do I test for empty date values in Power Automate?

You can use the empty() expression inside a Condition control. For example, empty(triggerBody()?['DueDate']) evaluates to true if the field has no value, allowing you to route the flow appropriately.

What causes the 'invalid parameter' error in the addDays expression?

The addDays function requires a valid timestamp string as its first parameter. If the dynamic content passed into it is null or formatted incorrectly, the function will fail and return an invalid parameter error.

Can I create a Planner task without specifying a due date?

Yes, the due date is generally optional in Planner. If your flow logic allows it, you can leave the due date field blank in the 'Create a task' action when a specific date is not provided.

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