Above you will see the shoulder belt on the passenger side rear that loops though the guide at the top of the seat. Remove the belt from the guide. This seat belt and the corresponding one on the drivers side will not be removed. We remove it from the clip for later removal of the seat-back cushion.
Above the center seat shoulder harness is integral to the 60% fold-down seat back. Do not remove the bolt at the bottom that secures it to the lap belt receptacle.
There is a bolt that holds the bracket for the seat belt receptacle to the floor and this bracket also secures the center shoulder belt to the car. Remove the bracket bolt in the center to the floor only!
Use a 14 mm socket with 6 inch extension.
Removing the bolt allows the shoulder belt to lift the bracket and seat belt receptacle.
Reinstall the bolt into the hole that it came from. This way you will not be looking all over the place for the bolt when you want to reinstall the seat back.
Moving to the passenger side there is a set of seat belt receptacles that you will remove the center bolt as you did above.
Then reinstall the bolt as you did above. Note that I have written on the metal brackets where they are positioned for when I reinstall the seats.
I take this loose part and a spare bolt and nut and connect it to the open hole in the other seat belt receptacle so all the parts stay together and not get lost for future reinstall.
As with the passenger side shoulder strap you leave this connection to the floor of the Prius there is no good way to remove the other end behind the rear inside panels and the belts will not be in your way.
We are done removing the seat belts. The next step is to remove the seat back cushions.