You can set this option at the global level and project level. Then CORE will prompt the user if they do not enter an expense memo.

To set the rule at the global level:

1. Go to Settings > Time & Expenses.
2. Under Expense Entry, select Expense entry memo required. This ensures that the expense entries of all new projects are not accepted without a memo.
3. Click Save. Check CORE Help Center for details. 

You can also set this rule at the project level:

1. Open the Projects screen and select a project on the grid.
2. In the detail view, go to its General > Assignment tab.
3. Click Add Rule and select Memo is required for expense entry.
4. Click Add and save the information. Check Assign Rules to Projects for details.