Unfinished Business (UB) unlocks at Rank 15 and can be accessed via the Office tab > top left corner. It consists of various stages, each offering different challenges. These stages can be completed by finishing missions within a specified time.
Plan your strategy accordingly by paying attention to the Bonuses and Penalties of the stage and the different choices in the Talent Tree. Try to finish as many missions as you can before the timer expires, this will give you more rewards.
There are 2 types of rewards you can collect from a stage.
1)Milestone Rewards: these rewards can only be collected once.
2)Mission Rewards: these rewards can be collected every time you play a stage.
After finishing a stage (or when the timer runs out), you'll be rewarded with Gear and Omerta Stones depending on the number of missions you have completed. Gear can be equipped by your capos, which gives them certain buffs (e.g. increase income or increase fight power). And Omerta Stones can be used to upgrade Gear. Note that Rings and Necklaces with 2 or more stars will have a unique additional bonus. Gear can be equipped, upgraded and removed on the capo profile page.
Are you stuck at a specific stage? Don't worry. Inside UB the last 2 stages you've played are automatically reopened every day. This allows you to collect new rewards every day!