The opening portion of the IP states:
The purpose of this daily inventory is to keep track of who we are and what we are doing today. Try to answer every question, every day. Keep your answers as simple and as honest as you can. If you miss a day, do not make it up later. Limit your answers and concerns to the past twenty-four hours and complete the questions at the end of the day.

The app has three menu items at the bottom of the main screen: Check in, Resources, and Profile.

Check In
This app provides a mobile version of a daily mini-inventory. You may scroll through the questions and answer them as appropriate. At the end of the questions, you have the option of saving your responses so you have an ongoing record of your responses, by date. Additionally, the app gives you the opportunity to add any upcoming events for the next day or in the near future.

Resources
On the Resources tab are links to NA's Meeting Search, the current day's meditation, as well as other options to call your sponsor, read literature, or financially contribute to the NA Fellowship. For the links to work properly, you will need to have internet access.

Profile
The last section is to keep track of your own information, including your clean date.