Dear English speakers,

When you say "you can't do that”. or "you sholdn't do that". as an advice not as a command, are there any differences between them?

I also would like to ask to whom you say them distinctively. (like I say "you can't do that”. to my friends but don't say that to my boss.)

1 Answer 1


The difference between these two is not in how polite they are, but in how strongly you want to express yourself. Either one says that there will be negative consequences from whatever the other person is being told not to do.

"You can't do that" expresses this more strongly, or with more certainty about the negative consequences of the action. "You can't do that" is more likely to be used if the consequences are simply failure to do whatever it is, or if the other person simply doesn't have the skills or authority to do it. "You shouldn't do that" is more likely to be used if the person has the ability to do it, but there will be some poor reaction or bad outcome from doing it.

Either one could be used with your boss, if you're in a situation where it's appropriate to advise your boss not to do something. Depending on the context and the boss's personality, it would be appropriate to use more softening language with either one, and to suggest appropriate alternatives. Such as

We probably shouldn't do that, because .... What I'd suggest instead is...


We can't do that, because.... What we can do instead is...

In these examples, I used "we" to refer to the whole organization, rather than "you" to refer just to the boss.

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