it is shipped or has been shipped

Question

what is the difference between these sentences, are they correct?

once it has been shipped, I will let you know how much I paid for the postage.

once it is shipped, I will let you know how much I paid for the postage.

Answer 1

They mean the same thing. One is the past participle as the adjective (a package that is shipped) and the other is the past perfect passive (a package that has been shipped)

You can do this sort of thing with many English verbs:

A meal that is eaten / a meal that has been eaten

An exam that is completed / an exam that has been completed

A question that is left unanswered / a question that has been left unanswered

Sometimes one sounds better than the other. Example:

Once the car is started, check the oil pressure again.

Here you can say once the car has been started, but with things like instructions, it's common to use simple, direct statements.

Again, there is no difference in meaning, so which you choose is usually up to personal writing style. Unfortunately I can't offer any rule to help choose which, except to say that the past perfect passive should be fine, if you can't decide.

Note that both of these are passive constructions. The subject causing the action is not as important as object being acted on, and is often omitted.

Once the new rules are submitted / have been submitted to the committee, they can be debated.

The passive voice allows us to avoid specifying who is submitting the rules, either because it's not important information, or because the writer doesn't want to say:

Let's just say that the window has been broken, and the cost of its repair will be paid by the person responsible.