In this article, the difference between the various date fields is explained:
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This is the delivery date of, for example, the sales order as it is created in an integration. vPlan takes over this date as the 'Due date'. In the case of a purchase order, this field may be filled with the expected delivery date of the order.
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This is a standard vPlan field that allows customers to indicate a 'deadline'. This field is available for customers without integrations to fill in freely. If you have an integration with Exact Online, this field is automatically filled with the same date as the 'Promised date'. It can then be adjusted in vPlan.
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The start date is a planned date. As soon as you place an order in the planning, for example on today, the start date is today's date.
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This is the end date of the planning. When an order is planned for one day, the end date is the same as the start date. So if the start date is February 11th, the end date is also February 11th. In vPlan, you can also plan an order over multiple days. For example, if you start the order today and it needs to be ready by Tuesday, you would have a start date of February 11th and an end date of February 15th.
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In summary: the start and end date represent your planning. The due date is a deadline date that is automatically filled in the case of integrations. You can use the due date in vPlan to set up notifications or to keep track of whether your delivery date is still being met compared to your planning.