What size hot wires neutral wire and ground wire do you need to feed a 200 amp single phase sub panel coming from a 400 amp service?

For a 200 amp single-phase subpanel, you typically need to use 2 AWG copper wire or 4 AWG aluminum wire for the hot wires. The neutral wire should be the same size as the hot wires, so 2 AWG copper or 4 AWG aluminum is recommended. The ground wire should generally be at least 6 AWG copper or 4 AWG aluminum, but it's best to consult local electrical codes for specific requirements. Always ensure compliance with local regulations and consider consulting a licensed electrician.