The shift to a floating net asset value has some practical implications for treasuries that invest in prime funds. Most importantly, instead of settling once a day at the end of the day, funds will have multiple strikes during the day.

Most fund managers have announced schedules with three strikes a day, at 8 a.m. or 9 a.m. ET, noon ET, and 3 p.m. or 4 p.m. ET. Companies will have to be aware of funds' schedules and time their redemptions according to when they need the money.

Tory Hazard, president and chief operating officer at trading portal ICD, cites the example of a company that wants its settlement to arrive during the morning. Assuming the first strike is at 9 a.m., the company would have to make a redemption trade by that time. "The fund will price between 9 and 10 or 10:30, and the corporate can expect settlement between 10:30 and 11:30," Hazard said. If the company wants its money during the afternoon, it could trade by noon to receive settlement between 1:30 and 2:30 p.m., or trade by 3 p.m. to receive settlement between 4:30 and 5:30 p.m., he said.