There are expenses that you know will end at a time in the future. These include childcare, and also expenses that will end when a child leaves the home or becomes emancipated.
Go to the line where you enter the expense, and click more info (the green 3-dots button in the Cloud software).
On the screen that appears, enter an end year for the expense.
For a final partial year, you may override the expense in the final year, at the bottom of the page.