Date: 202011
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class E ZZZ
ATC / advisory: Center ZZZ
Second aircraft: Commercial Fixed Wing
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Developmental
Human factors: Communication Breakdown; Confusion; Human-Machine Interface; Situational Awareness
Anomaly: ATC Issue All Types; Airspace Violation All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance
Contributing factors: Environment - Non Weather Related; Human Factors
Primary problem: Environment - Non Weather Related

Narrative: The incident with Aircraft X can best be described as the perfect storm where in this case the R-side Controller working [two sectors] was very busy and on top of that had numerous aircraft that departed ZZZ Approach level at 160 in his airspace without communication. Prior to me sitting on his position he reached out to the Supervisor to request a D-side along with advising that ZZZ Approach was not shipping aircraft in a timely manner. One aircraft he had was Aircraft Y who was 53 miles into his airspace level at 160 still not on frequency and Aircraft Z; 23 miles into his airspace with the same issue. I mention this because I believe this was the biggest contributing factor to the event with Aircraft X. Aircraft A was at 160 and he descended the aircraft to 10;000 thinking he was a ZZZ1/ZZZ2 arrival and to alleviate all potential traffic conflicts. The main problem was as soon as I sat down and signed in; the R-side was too busy to give me a brief but I was eager to help and to catch up on anything. As I was beginning my scan I noticed Aircraft X getting close to the ZZZ1 Approach airspace at 10;000 without a hand-off and I immediately jumped on the line to coordinate with the ZZZ1 Approach Controller. I began to try to APREQ the aircraft at 10;000 but the ZZZ1 Controller realizing he had an arrival to ZZZZZ [Intersection] already at 10;000 he instructed me to descend Aircraft X to 080; the R-side complied. There was no loss of separation between any aircraft; however; I have decided to report this event because I was talked to by management because of it. I advised my Supervisor in the X area that I did the best I could given I had just sat down and had just noticed the aircraft not handed off to ZZZ1 Approach. Given the coordination could have been done in a more efficient and timely manner I had to work with what I had.According to the safety board's review of the event there was an airspace violation as a result of this coordination. In my opinion this happened because the ZZZ1 Controller and his uncertainty of what needed to be done. I offered to descend Aircraft X to 080; but he advised me to just leave him at 10;000 and then instructed another aircraft to descend below the Aircraft X flight. This back and forth coordination and being reluctant to take the hand off is what resulted in Aircraft X entering his airspace without a hand off. I would like to add that overflights are not allowed over ZZZ NAVAID per our LOA; however the situation dictated a different solution. I would also like to emphasize that as the D-side Controller in this situation had I not immediately gotten on the line with the ZZZ1 Controller this would have been a much different and ultimately worse issue. I am almost certain a loss of separation would have occurred. My Supervisor agreed and the R-side backed me up on it. I have chosen to report this event because even though management advised me this was not disciplinary in any way shape or form; I would still like to bring this up to the safety council's attention.Because of COVID; staffing has been an issue and the traffic volume was high. We had staffing later in the day that helped tremendously but this particular situation we were at minimum. I would also like to receive guidance as to what I could have done better given I was forced into a bad situation and I did my best to separate aircraft and coordinate what I could before an incident may have occurred.




Synopsis: Center Controller reported an airspace violation due aircraft hand-off issues with a TRACON facility.