The pilot of the helicopter reported that while flying at an indicated altitude around 200 to 300 ft, while on approach to land at an off-airport landing zone, he saw a black “drone” [unmanned aerial system (UAS)] in front of his windscreen. He attempted to avoid the UAS but was unable and the UAS impacted the main rotor resulting in substantial damage to a main rotor blade. The pilot reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation. The UAS operator reported that he was conducting operations over a construction site. The area was inside of the class C airspace of a nearby airport and the UAS operator was using a Federal Aviation Administration Certificate of waiver or authorization (COA) that had been previously obtained by the construction company who hired him. The UAS operator reported that he was flying at an altitude of 180 ft, and that before the flight he had not realized that this altitude was above the maximum altitude of 150 ft imposed by the COA. The COA also required the UAS operator to notify the air traffic control tower at the nearby airport at least 15 minutes prior to the proposed start time of any operations. The UAS operator stated, and a review of contact records by the air traffic control tower confirmed, that no call was received from the UAS operator notifying them of the operation. Additionally, the drone operations manager for the construction company who contracted the UAS operator reported that the operator was supposed to check in with the on-site supervisor before conducting operations and stated that this did not happen on the day of the accident.