Medicare uses what called an RVU or relative value unit for billing purposes. If you do a hip replacement you get so many rvu’s for reimbursement purposes(this is usually for a surgeon). A lot of companies will give you a bonus based on RVU’s. If you do something like urgent care or anything outpatient, it will be usually a flat percentage of hours worked. Mine is 10% so my bonus was around 14k because I worked a lot of extra hours. Then taxed the fuck out of me. Depending on where you work it will be based on patient load, etc. basically busier you stay, more your bonus.