The first location where you disconnect the utility to facility wiring is called the Service Disconnect. Within the Service Disconnect Enclosure, you need to bond the neutral and equipment grounding conductors, which is done with the Main Bonding Jumper. This is the only location in the system where they are bonded - In any subpanels, the neutral and equipment grounding conductors are NOT bonded. Within the Service Disconnect Enclosure, it would be OK to land neutral and equipment ground conductors on the same busbar. The busbar would be considered the Main Bonding Jumper.

Your panel is considered the Service Disconnect in this system. Therefore it would be OK to land both on the same busbar. However, if you had an upstream disconnect, this would be consider a subpanel, and the neutral and equipment grounding conductors would need to be isolated.

As a result, it's good practice to typically land neutrals and equipment ground conductors on separate busbars. 1 - If you were ever to add an upstream panel for any reason, you would have to modify all the conductors in this panel if they were mixed. 2 - If you're in the habit of separating these conductors, you don't make the mistake when installing a sub panel which DO need to be separated. 3 - There are inspectors who don't like them to be mixed on the same busbar (subjectively). For all these reasons, most electricians separate them on all panels they wire.

FWIW, there are a ton of terms that are used in grounding & bonding that mean different things, and even savvy folks interchange them incorrectly. I'm sure I mixed terms above. Haha.

9 times out of 10, if not more, a panel is not used as service equipment, and needs separate N and G bus bars. It's easier to make panels with separate bars and add jumpers as needed.

We've got some great knowledge on this board.