In my 2014-built United States mainland home, I have two side-by-side 200A panels. They both have a 200A main breaker. One really neat thing this let me do is have two lighting circuits in the basement, so that I can work on a panel with the main off and have great lighting to see what I'm doing. There are of course, no loads that pull from both panels.
Both panels receive power from the same meter can on the other side of the wall,which I believe is rated 320A. The meter can does not have a breaker. The meter can is designed with one input and two outputs for each conductor. I believe the meter can is a Milbank U4702-X-5T9-K3-K2-IL 
In both panels, the ground and neutral are bonded together as they should be in a main panel.
Obviously both of the neutrals come out and tie to the same lug under the meter. And both of the ground wires coming out of the tandem main panels are tied to the same building steel and grounding rods.
My question is this: Why isn't Neutral-to-Earth bonding done in the meter can in a "class 320" service? (before it splits off to two separate panels)
Is it just that the interior of the meter can isn't as inspect-able as the interior of the panels?
The two main panels are in some way sub-panels of the meter can right? I read all the time neutral and ground should only be bonded in one place. I understand why if I hang a sub panel off a main it should be isolated there. But why would the same logic not affect my tandem main panels?
Best Answer
In my neck of the woods (Pacific NW) we call that a "class 320" service: A single meter feeding 2 main panels. Because both panels are considered main panels, neutral and ground need to be bonded together. In the meter panel, in most cases, the neutral is already bonded to the can just by how the lugs are attached. I recently installed a class 320 service on my son's house that did have a "service bypass" that would enable the power company to swap a meter without interrupting service, but I don't think that is what you have. A pic would help.
2020 code is requiring the ability to cut off power to a structure externally. That may have been required locally for some reason back in 2014...local codes vary.