If your app is going to offer in-app purchase then you will need to accept the iOS Paid Applications Contract in your iTunes Connect account.
To do this please follow the process below.
1. Sign into your iTunes Connect account with your username and password: http://itunesconnect.apple.com.
2. Click on Contract, Tax and Banking from the menu page.
Click "Set Up" to setup your Contact, Bank and Tax information. Do this for the first row.
After you have done that, your screen should look like this:
If you encounter any problem doing this please let your Support/Account Manager know. Also let them know once it has been done so that they can proceed with the setup and submission process.