EMB145 flight crew reported rejected takeoff when first officer's seat slid back.

Attributes
ACN	1752265
Time
Date	202007
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	EMB ERJ 145 ER/LR
Operating Under FAR Part	Part 121
Flight Phase	Takeoff
Flight Plan	IFR
Component
Aircraft Component	Pilot Seat
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 10 Flight Crew Total 1200 Flight Crew Type 50
Person 2
Function	Captain Pilot Not Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 10 Flight Crew Total 3000 Flight Crew Type 2500
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy

Narrative:

During the takeoff roll at approximately 100kts my seat; first officer (first officer) seat; slid all the way back. The captain called for the reject and we performed a rejected takeoff. First officer seat slid back beyond ability to reach controls.seat not secured in place properly.it was an abnormal situation; both pilots deemed it unsafe for flight; and rejecting the takeoff was the safest action.

Original NASA ASRS Text

Title: EMB145 flight crew reported rejected takeoff when First Officer's seat slid back.

Narrative: During the takeoff roll at approximately 100kts my seat; FO (First Officer) seat; slid all the way back. The Captain called for the reject and we performed a rejected takeoff. FO seat slid back beyond ability to reach controls.Seat not secured in place properly.It was an abnormal situation; both pilots deemed it unsafe for flight; and rejecting the takeoff was the safest action.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.