Short version: owning several accounts stays allowed. Playing them in different leagues stays allowed. From the season that starts on 14 September, actively playing more than one of your accounts inside the same league is not allowed, and any account involved can be banned, not only the newest one.
Because of the abuse it makes possible. That is the whole reason, so it is worth being blunt about it.
Almost every form of cheating we have had to act on this year needed two accounts in one league to work at all. Attacking your own second account for gold and experience. Keeping a weak account next to a target so there is always something safe to hit. Passing the same cities back and forth. Filling a clan with your own accounts to pull in gift after gift. A free scout that costs you nothing because it is your own troop. And on top of all that, a second account in the same league quietly doubles your daily and weekly gifts, your mission board, your event currency and your clan slots, in the one ladder where you are being ranked against everybody else.
We have spent this season building measures against those patterns one by one: rewards that notice when your progress comes from your own side, a brake on cities being swapped between the same two players, action against gift farms. Every one of those measures exists because of the same setup. Cutting it off at the root is worth more than another layer of counter measures on top.
There is nothing wrong with the second account itself. In a different league it costs nobody anything, and you are welcome to keep playing it there.
Not allowed from 14 September: actively playing two or more of your own accounts in the same league.
Still allowed: owning as many accounts as you like, and actively playing them in different leagues. Bronze, Silver, Gold and above are separate ladders, and an account in each is fine.
Still not allowed, as before: using your accounts against each other, wherever they are. Attacking your own account, moving troops, cities or resources between them, or scouting with one for the other, has always been a violation and stays one.
Living in the same house as another player. Sharing wifi, or a phone, with family or friends. Two people in one home, each playing their own account, have never been a problem and still are not.
A shared connection on its own tells us nothing, because entire households and whole mobile networks share one address. What we look at is whether one person is playing both accounts: the same device, effectively the same name, movements between the accounts, and sessions that hand over from one account to the other, evening after evening.
Cases are reviewed by a person, never by an automatic ban. When it is clear that one player is running several accounts in one league, any of those accounts can be banned, including the main one. Keeping your oldest account safe by parking the rule breaking on a newer one is not going to work.
If you are playing more than one account in one league right now, pick the one you want to keep there and move the others to another league, or stop playing them. Nothing you have done so far is being punished retroactively: the rule applies from the new season.
If you are not sure whether your situation counts, ask support before the season starts rather than after. A question costs you nothing, and an honest household is never the target of this.
The Code of Conduct and the Terms of Use have been updated with the new rule.