Why was an employee's application auto-rejected? For UK only

When an employee submits a Holiday Trading application and an approver amends it (for example, the employee applies to buy 5 days but their employer approves only 3 days) the employee will receive a notification email that their application was amended at the time the amendment takes place. 

It is the employee's choice whether to accept the amendment or to reject it (for example, to accept to buy only 3 days instead of 5, or to cancel the 5 days they've applied for and not buy any days at that time). The employee will have until the cut-off date (pre-to decide and action the amendment). They will also receive a reminder (email notification) a day before the cut-off date if they haven't taken any actions from the time of the amendment to that moment. 

If the employee does not take any action (neither accepts nor rejects the amendment), then at the cut-off date their application will be automatically rejected. 

Why would the product automatically reject the amended application at the cut-off date?

The product cannot automatically accept the application of the employee in case the employer disagrees with the initially submitted number of days/hours by the employee.

It also cannot accept any amendments to the application of the person who submitted it (the employee) by another person (the employer), without the confirmation of the employee.

First deductions of all approved applications are due at the cut-off date, that's why, if there are amended applications that were not approved or rejected, they are automatically rejected by the product.

How can an employee approve or reject their amended application? 

There is a link to the Order History page on the product page, here employees can see the historical data of their applications. They will also find the amended application here and can either approve or reject it. 

Another way to do it is to follow the link in the email notification they will receive.