I will let you know once done.

[Talab1234]

I will let you know once done.

Is it ok to omit “it’s” here?
Context: letting someone know once a task (it) is done.

 

[5jj]

No.

 

[Barque]

Is it ok to omit “it’s” here?

The omitted word could be either "it's" or "I'm".

What do you mean by "ok"? If you mean "grammatical", no. If you mean "Is it likely to be used?", yes.

 

[5jj]

I would not say that it's very likely to be used.

 

[Barque]

If you mean "grammatical", no.

On second thoughts, if the omitted word is "it's", I'm not sure omitting it would make it ungrammatical. I suspect not everyone will agree.