The PNO handles Hart-Scott-Rodino Premerger Notification Filings for well over a thousand transactions each year. Each transaction requires the acquiring person to pay an HSR filing fee, which must be paid within two days of filing an HSR Form in order for the HSR waiting period to begin. If payment isn’t received on time, the PNO will "bounce" the filing as incomplete and delay the start of the waiting period.
The FTC has recently made some changes that will make it easier to get your HSR filing fee to the agency. This blog provides an overview of what’s new.