Should I tell my boss I'm interviewing internally?

If you don't, you can kiss the position goodbye. There's no way they'll respond positively to a blatant disregard for policy like that.

Always be upfront and honest, rule #1

There's no way they'd ever want to hear your current boss' opinion about you. Obviously having the right conversation with your boss, where he'd be willing to go to bat for you, would also do you a disservice... Talk to him, it'll probably help you land the position.

First off, since its firm policy to disclose any internal interviews with your manager, you should definitely tell him. Second, if you have a good relationship with your boss, having him in your corner would only help you

This is more of a gray area in certain circumstances, but if it is your firm's policy to disclose, then why the hell are you even asking?

I think it depends on your relationship with your boss and the type of person he is. He might feel that you're a traitor for leaving to equities and if you don't get the new position, he will treat you worse going forward. I think that you should you should tell him when you have more confidence that you will be able to move. Your firm policy might say to notify your boss but it might not indicate when you should do so.

Sounds like you don't want to have an uncomfortable conversation with your boss. Better to get it out of the way now than after he finds out from someone else.

Keep in mind, the first person that the hiring manager will talk to if this is an internal role, is your boss.

There are no thoughts, discussions or other opinions. Go talk to your boss, let him know you are interested in the opportunity and plan to apply. Imagine what will happen when your boss gets blindsided by someone calling to get an opinion on you? That's a quick way to torpedo the opportunity before it even starts. At the very least, it looks awful to go around him like that if you end up staying and not getting the job.

I'd evaluate your relationship with your boss if you have to ask about discussing that with him.

Yes you should.

Tell him no matter what his opinion of you.

My guiding principle in business is very simple: it is always about the people you work with. Sure money matters a lot, and the type of work matters too. But with all things somewhat equal, you should with the best people.

If your boss likes you: if he could to bat for you (more likely), or he could try to keep you in (which is not bad since that would give you some leverage to dictate your work)

If he hates you: you are probably helping him getting rid of you, and he might forget about his misery soon anyway. And, if that's the case, you know you shelf life in the company was already limited.