Several of the Gate Encounter cards involve skill checks stated in such a way that I'm not entirely sure whether they're optional or mandatory.

Gate Encounters with skill checks seem to fall into these categories:

1) "Make a [skill check]. If you pass, [good outcome]. If you fail, [bad outcome]." This is clearly mandatory.

2) "Pass a [skill check] or [bad outcome]." This is also clearly mandatory if I don't want to suffer the negative outcome.

3) "You may make a [skill check] to [flavor text]. If you pass, [good outcome]. If you fail, [bad outcome]." The word "may" clearly makes this an optional check. You can discard the card as if you had no encounter at all.

4) "Pass a [skill check] to [good outcome]. If you fail, [bad outcome]." This is the one I'm hung up on. We've been treating these as mandatory because of the imperative, "Pass a …," but now I'm not so sure. Because it's phrased as "do this to get that," it sounds like I might be able to decide getting "that" isn't worth the risk of the negative outcome. Do I have to attempt these skill checks, or can I opt out of them as if they were "You may make a…" encounters?

Here are some actual examples from the base game:

Blue Other encounter: Pass a Fight (-2) check to lever back the lid of the stone chest. Inside, you find $8. If you fail, lose 1 Stamina.

Blue Dreamlands encounter: Pass a Luck (-1) check to tour the golden spires of Thran, gaining 2 Clue tokens in the process. If you fail, stay here next turn.

Green Great Race encounter: Pass a Sneak (-1) [2] check to draw 1 Unique Item and return to Arkham. If you fail, your captors are none too kind. Lose 3 Sanity and 1 Stamina.

Thomas Cartwright said:

All of those quoted are mandatory for my take.

Dam said:

Seconded. Unless it's stated "you may" / "if you decide" / "if you accept" (or a similar wording is used), encounters are mandatory.

Thanks for the confirmation. I figured we'd been playing it correctly but had a moment of doubt.

The real question for me is the encounters that say "pay $X for X effect," some of which say "if you can't or won't pay, X happens".   Does this second clause imply that not paying is always an option in such encounters.

Not paying is an option in that particular encounter, since it says "won't." I can only think of one such encounter that tells you up front, and then says you can opt not to, so it shouldn't be a big deal.

Can't remember where I read this now, but hasn't it similarly been clarified that you can opt to not pay the $1 interest on your bank loan (and take the consequences of defaulting), even if you have the $1 on hand?

Thomas Cartwright said:

Not so sure I get your point. Bank loan: "Roll a die. On a 1-3, pay $1 or discard all of your items along with this card. " It's not: "On a 1-3 pay $1. If you don't have enough money, then discard all of your items along this card". So, yes, you can choose which of the two.