AccountancyManager has a feature called Missing Deadlines where you can check if any deadlines are missing for clients are prospects. To access this, go to Tasks > Missing Deadlines.
You can use the Prospects and Clients deadline to view more detail. If a Service is turned on but no deadline has been added then the Task will be missing from your Task List. As with the Recurring Task list, you have the show, search, sort, and previous/next options to sort, search, and navigate the missing information.
Click the Client/Prospect name on the left to navigate to their client file and add the Missing Deadline.