Good day,
The BER requirement varies based on the standard (as per your comments). Generally a BER of 1E-12/1E-15 is specified for telecommunication grade systems (low latency and high bit rate 10 Gbps/100 Gbps). For WiFi and free space systems the requirement is usually between 1E-6 up to 1E-12 (the requirement varies based on the application area, such as low bit rate systems or when a certain level of packet loss is tolerated). Also many many systems these days (such as the new WiFi standards) employ advanced error coding which will bring a system operating even at 1E-3/1E-4 up to 1E-12/1E-15 and higher.
For your design work I would say 1E-9/1E-10 is a good metric to work from (it’s quoted frequently in text books).