In EZPerDiem, substantiating is optional, but recommended.  Substantiating means that you properly record an expense.  It is one thing to say you had $200 in van driver tips last year.  It is another to have them properly written in a format that shows when they occurred, how much they were, and why they are deductible.  The latter is what will stand up to IRS scrutiny if you are ever audited.

EZPerDiem makes it simple to substantiate your flight crew expenses.  Just click on the expense icon next to the date of an expense on the Layover Entry Page.  This will open a window that will allow you to enter all of the those details.