What happens if you don't pay? The consequences are aggression, and the fact that threat is hanging over you makes taxes a form of aggression. Coercing is a form of aggression.
Letting someone starve is aggression. If you have to work for minimum wage because the alternative is homelessness, isn't that also a form of coercion?
You get charged interest. Then, you might have your wages garnished. If that isn't sufficient, your bank accounts might get frozen. If that still isn't sufficient, liens.
I wasn't aware of that; I don't consider myself an anarchist really. I just think it's more like what Heinlein wrote, that violence is the supreme authority from which all other authorities are derived. I'm not sure I like it but I do think it's rather true. Almost everything can be traced back to some form of this.
Note the 'almost'. I'm sure some outliers exist but that's not what we're talking about.