Skończenie raportu przed spotkaniem jest ważne.

Skończenie is a verbal noun (sometimes compared to a gerund-like form in English). It comes from the verb skończyć = to finish / to complete.

In this sentence, it works like a noun, not like a normal verb:

• skończenie raportu = finishing/completing the report

Because it is a noun, it can be the subject of the sentence:

• Skończenie raportu przed spotkaniem = the thing that is important

It is also a neuter singular noun, which matters for ważne later in the sentence.

Because after a verbal noun like skończenie, Polish normally uses the following noun in the genitive case.

So:

• skończyć raport = to finish the report (with the normal verb)
• skończenie raportu = finishing/completion of the report (with the verbal noun)

That is why raport changes to raportu.

A helpful way to think about it is:

• literal structure: the finishing of the report

The preposition przed here means before, and in this meaning it takes the instrumental case.

So:

• spotkanie = meeting
• spotkaniem = instrumental singular
• przed spotkaniem = before the meeting

This is a very common pattern:

• przed obiadem = before lunch
• przed pracą = before work
• przed egzaminem = before the exam

Because ważne has to agree with the grammatical subject, which is skończenie raportu przed spotkaniem.

The head of that subject is skończenie, and skończenie is:

• singular
• neuter

So the adjective is also neuter singular:

• ważne

Compare:

• Raport jest ważny — raport is masculine, so ważny
• Sprawa jest ważna — sprawa is feminine, so ważna
• Skończenie raportu jest ważne — skończenie is neuter, so ważne

In a normal full sentence, jest is the standard and natural form.

So:

• Skończenie raportu przed spotkaniem jest ważne. = normal standard Polish

If you remove jest:

• Skończenie raportu przed spotkaniem ważne.

that sounds incomplete, telegraphic, or stylistically marked. You might see omission in headlines, notes, or very informal shorthand, but not as the normal full sentence here.

This is about aspect.

• skończenie comes from skończyć, a perfective verb
• kończenie comes from kończyć, an imperfective verb

The perfective form focuses on completion:

• skończenie raportu = getting the report fully finished

The imperfective form focuses more on the process/activity:

• kończenie raportu = the process of finishing / working on finishing the report

In this sentence, the idea is that the report needs to be completed before the meeting, so skończenie is the more natural choice.

Yes, ukończenie raportu is possible, and it also means completion of the report.

The difference is mostly one of style and nuance:

• skończenie = more everyday, common
• ukończenie = often a bit more formal or bookish

For a report, both are understandable, but skończenie raportu sounds very natural in everyday Polish.

Yes, but the sentence structure would usually change.

Natural alternatives include:

• Ważne jest skończyć raport przed spotkaniem.
• Ważne, żeby skończyć raport przed spotkaniem.

These are both common.

What is less natural is putting the infinitive first as the subject:

• Skończyć raport przed spotkaniem jest ważne.

That is understandable, but it sounds less natural than the versions above. Polish often prefers either:

• a verbal noun as in your sentence, or
• a structure like Ważne jest... / Ważne, żeby...

No, Polish word order is fairly flexible because the cases show the grammatical relationships.

Your sentence:

• Skończenie raportu przed spotkaniem jest ważne.

is a normal, neutral order.

Other possible orders are:

• Ważne jest skończenie raportu przed spotkaniem.
• Przed spotkaniem skończenie raportu jest ważne.

These versions shift the emphasis:

• starting with Ważne emphasizes the judgment
• starting with Przed spotkaniem emphasizes the time frame

But the original version is clear and natural.

It describes skończenie — in other words, the finishing happens before the meeting.

So the structure is:

• [Skończenie raportu] [przed spotkaniem] jest ważne
• Finishing the report before the meeting is important

It does not mean that the report itself is somehow before the meeting. The time phrase attaches to the action/event expressed by skończenie.