In general, honestly is the best rule. But there are several situations when you rather better not to tell the truth. When you’re:
1. Protecting Colleagues
If you've got personal dirt on your colleague, you owe it to them to keep quiet, even if the boss asks.
For example, if you know that John is sick because of the party last night, it is not your responsibility to be the office tattletale.
In business, you're well advised to mind your own. And if it's not your own business, leave it to somebody else to dish the dirt. Just say "I have no idea." Even if you do.
2. Job Hunting
You have a right to look for another job without suffering the consequences.
Sometimes you might even get fired before you find the job you want because your boss figures that you're planning on leaving anyway.
Sometimes you've got to look out #1, so feel free to tell any lies that are necessary to keep your job-search secret.
3. Boss Ask You About Their Appearance
Bosses, like anybody else, can be vain about their appearance and it's natural for them to ask for advice.
When it comes to your boss appearance, it's best to keep your opinions and suggestions for improvement to yourself.
For example, if your boss wore something that look ridiculous rather better keep your mouth shut.
4. Boss Tell You Bad Jokes
Each boss thinks that underlings have to laugh at your jokes.
Even boss have already told you the joke ten time and it doesn’t sound funny, you need to emit at least some kind of chuckle.
Yeah, it's a bit degrading, but think of it this way: at least your boss is trying to be entertaining. The way I see it, any attempt on the part of the boss to act like a human being should probably be encouraged.
And what's it really costing you?
Note: don't overdo it or you'll sound sarcastic.
5. Boss Stupidity Creates More Work for You
Sometimes bosses just plain get in the way. When that happens, it's your job to keep them out the way, even if it means a little lying.
For example, your boss have new plans which would require you to work 100 work weeks to implement. If your boss is the type who's unwilling to budge on deadlines, you are 100% justified in simply saying that the new features are "impossible" to implement.
In other words, you work for your boss, but you do not owe it your boss to make it easier for him to make your job pointlessly more difficult.
6. You'll Pay a Penalty for Truth-Telling
Often bosses can't handle the truth, they don't really want to hear it.
For example, if some strategies of sales does not work, but your boss is sure this is the best way to sale products than you have no chances to convince him otherwise.
They'll figure it out sooner or later ... hopefully after you're long gone.
7. It's None of the Boss's Damn Business
If your boss decides to ask you on your religion, your politics, your personal life, your sexual orientation, your eating habits, or anything else that doesn't directly affect your work performance, you have no obligation to answer truthfully.
You have every right to keep anything and everything about your personal life entirely secret from your boss.