The job this tool does, and who does it today
An incentive plan has two jobs. During the month it should tell a rep what to do differently. At the end of the month it should produce a number nobody argues with. Most plans fail at both, and for the same reason: the calculation lives somewhere the rep cannot see.
In practice the work is done by a sales coordinator or an admin with a workbook. They export orders from the billing system, paste them into a tab, apply a slab table somebody built two years ago, adjust for the deals finance flagged as uncollected, and email a figure. Reps who question it are shown a screenshot. Reps who question it twice are told the plan is complicated.
A sales commission calculator's real job is provenance. The arithmetic is simple; what matters is that every rupee of payout can be traced back to a specific deal, a specific collection status and a specific published rule.