As a runner, can you use New Angeles City Hall to avoid tags on the Corp's turn before he can trash it?

I looked at the timing page in the FAQ and it says paid abilities are used before the Corp's turn begins, then after that there are no paid ability windows until the Corp's first turn.

So I'm not sure how this would work. Thanks for clarifying!

Avoid and prevent abilities trigger differently then regular paid abilities. So yes you can avoid a tag that activist support gives you with NACH.

From the rulebook:

"

Some card abilities use the words “prevent” or “avoid.” Prevent

or avoid effects are the only effects which can disrupt another

effect. A prevent or avoid effect states what it is preventing

or avoiding, and an effect that is prevented or avoided is not

resolved. Prevent or avoid effects can be triggered whenever the

effect they are preventing or avoiding is resolving."