Follow Change the  information displayed at  https://proconnect.intuit.com/community/help-articles/help/adjusting-user-options-in-lacerte/00/5190

Select Due Date from Client Information Group on the left then click the > to add it to the list. It may already be in the list, if so, move it up to where you want it. Click OK

NOTE: Often this is not correct until you have "processed" the return. Either look at views form OR Highlight the clients and select Client > Update Client Database. This sometimes happens after updates, especially if the 15th falls on a day off.