My 100 amp panel has a 4 wire feed. 2 hot wires to the 100 amp breaker and the netural and ground wire go to the same ground bar which is grounded to the panel. I this correct or should there be a separate ground and a separate netural bar? The panel is original to the house built in 1987. The 100 amp panel is fed from a 200 amp panel in the other side of the house put in about 8 years ago to feed a hot tub and other things

Grounding was a bit misunderstood back then, and still is a bit.

What is needed is an accessory equipment grounding bar/terminal strip, bolted to the panel box with machine screws.

Have all bare and green equipment grounding conductors connected to the new bar.

Be sure to remove any bonding screw or jumper that connects the neutral bar to the metal box of the panel.

This was the main panel when the house was built. It looks like the electrican did do the whole job when he put in a new 200 amp main and made the 100 amp panel a sub panel.

The fact that it was the original main panelboard does not change the previous answer.

The 100 amp panelboard requires a four wire feed from the 200 amp panelboard.

At the 100 amp panelboard, Neutral and Ground must be separated. That is why T.K. told you to remove the screw.

Neutral conductors must connect to the Neutral bus and Ground wires must connect to the Ground bus in the 100 amp panelboard.

By the electrical code, the ONLY place that ground and neutral can be joined together is at the main panelboard.

Don, only at the Main Service Disconnecting Means, not the Main Panel.

Does a 100 amp sub panel need a main breaker?

Only if located in a separate building.