Light Transport
Flight Crew Commercial; Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 125; Flight Crew Total 2200; Flight Crew Type 1285
Communication Breakdown
Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
General None Reported / Taken
Environment - Non Weather Related; Human Factors
Day 1 of the cycle I was arriving in ZZZ to meet up with my First Officer (FO) for flights that afternoon. I came on duty and was scheduled to land in ZZZ this afternoon. I was in contact with my original FO who was home on standby in the morning and was coming to the airport this afternoon for our flights. When I landed in ZZZ; Flights Operations informed me my original FO had been taken off of the flight-line due to COVID. Flight Operations informed me I had another FO coming in to replace him and I should be able to maintain my original departure time out of ZZZ. I was texting my new FO asking when he would be at the airport and he said around XA30. In the meantime I got the airplane ready; so that we could depart as soon as he arrived. When he arrived we called Flight Operations to confirm our flights and then we took off. The next day; Flight Operations reached out to my FO and told him that we had taken off while he was in FAR rest period. I had no idea he was still in rest; I was under the impression he was already on duty as home standby and had been called in for the flight. Upon finding this out I called the Chief Pilot's Office and explained the situation.Looking forward; I'm going to confirm the FO's duty start time so that we are all on the same page and staying legal within flight duty.
Corporate Captain reported the original First Officer (FO) was replaced because of COVID-19 and the replacement FO was still in FAR rest period when the flight took off.