The 4 Categories to Calculate ROI Automated billing finds you income that manual processes miss. For our calculations, we assume that monthly billing is $50,000 and that missed billable events and errors account for 3% of that total. So, the total cost of under-billing errors is $1,500 per month. This figure is added as additional billable activities to the savings calculated in the tables. For the example calculations below, we show implementing a WMS to save 6 hours daily in billing, bringing the total time spent on customer communications to 2 hours each day instead of 6. extensiv.com | 833.983.6748 12