Ходатайство нужно подать сегодня.

Because нужно commonly combines with an infinitive to express that something needs to be done.

So the structure is:

[thing] + нужно + infinitive

In this sentence:

• Ходатайство = the petition / motion / application
• нужно = it is necessary / it is needed
• подать = to submit / to file
• сегодня = today

Literally, the Russian is something like:

The petition is necessary to submit today.

More natural English: The petition needs to be submitted today.

This is a very common Russian pattern:

• Мне нужно уйти. = I need to leave.
• Документы нужно проверить. = The documents need to be checked.

Here нужно is not acting like the short adjective needed agreeing with a noun. Instead, it is being used as an impersonal predicative word meaning:

• it is necessary
• it is needed

That is why it stays in the fixed form нужно.

Compare:

• Мне нужен врач. = I need a doctor.
  Here нужен agrees with врач (masculine singular).

But:

• Мне нужно позвонить. = I need to call.
  Here нужно means it is necessary and goes with the infinitive.

In Ходатайство нужно подать сегодня, it is the second type: impersonal нужно + infinitive.

It is in the accusative case, as the direct object of подать.

However, ходатайство is a neuter inanimate noun, and for many neuter inanimate nouns, the nominative and accusative forms are identical. So it looks the same in both cases.

• Nominative: ходатайство
• Accusative: ходатайство

So even though the form does not change, its function in the sentence is: the thing being submitted.

Russian word order is much more flexible than English word order. Putting ходатайство first often gives it topic or emphasis status: we are talking specifically about the petition.

This sentence could also be arranged as:

• Нужно подать ходатайство сегодня.
• Сегодня нужно подать ходатайство.
• Ходатайство сегодня нужно подать.

These are all grammatical, but the emphasis changes slightly.

Very roughly:

• Ходатайство нужно подать сегодня.
  As for the petition, it needs to be submitted today.

• Сегодня нужно подать ходатайство.
  Today is the important part.

• Нужно подать ходатайство сегодня.
  More neutral, focusing on the action.

Russian word order often reflects information structure rather than strict grammar rules.

Подать is the perfective form, while подавать is imperfective.

Here, the sentence is about completing a single action: submitting the petition. That is why perfective подать is the natural choice.

• подать = to submit / file (as a completed act)
• подавать = to be submitting / to submit repeatedly / in process / in a general sense

Since the sentence says сегодня, there is a concrete deadline and a one-time result is implied. Russian strongly prefers the perfective here.

Compare:

• Ходатайство нужно подать сегодня.
  The petition needs to be submitted today.
  (one complete action)

• Ходатайство нужно подавать заранее.
  The petition needs to be submitted in advance.
  (general rule / repeated situations)

It is an impersonal construction.

Russian often expresses obligation without explicitly stating who must do the action. English often does something similar with phrases like:

• It is necessary to...
• It needs to be...

In Ходатайство нужно подать сегодня, the sentence does not say who must submit it. The focus is on the necessity of the action itself.

If you wanted to specify the person, you could add that:

• Мне нужно подать ходатайство сегодня. = I need to submit the petition today.
• Вам нужно подать ходатайство сегодня. = You need to submit the petition today.

Yes, in many situations you could say:

Ходатайство надо подать сегодня.

This would mean almost the same thing.

In everyday Russian, надо and нужно are often very close in meaning:

• надо = need to / have to / must
• нужно = need to / it is necessary

A rough tendency:

• надо can sound a bit more conversational.
• нужно can sound a bit more neutral or slightly more formal.

But in many real contexts, the difference is small.

Yes. For example:

Ходатайство должно быть подано сегодня.

This is more formal and more clearly resembles English must be submitted or is to be submitted.

Compare the styles:

• Ходатайство нужно подать сегодня.
  Very natural and common.

• Ходатайство должно быть подано сегодня.
  More official, formal, bureaucratic, or written.

Since ходатайство itself is already a somewhat formal word, both can fit, but нужно подать is often simpler and more conversational.

Yes. Russian allows сегодня to move around, depending on emphasis.

Possible versions:

• Ходатайство нужно подать сегодня.
• Сегодня нужно подать ходатайство.
• Нужно сегодня подать ходатайство.
• Ходатайство сегодня нужно подать.

All are possible, but they do not sound equally neutral.

The most neutral options are often:

• Сегодня нужно подать ходатайство.
• Ходатайство нужно подать сегодня.

Placing сегодня first usually emphasizes the time: Today is when this needs to happen.

Placing it at the end often makes it sound like new information: The petition needs to be submitted today.

The main stresses are:

• хода́тайство
• ну́жно
• пода́ть
• сего́дня

So the full sentence is:

хода́тайство ну́жно пода́ть сего́дня

A learner may especially want to notice:

• the stress in хода́тайство is on да
• the stress in сего́дня is on го

Stress in Russian is important because it is not always predictable.

Not exactly. Russian does not need a dummy subject like English it in sentences such as It is necessary to...

English says: It is necessary to submit the petition today.

Russian simply says: Нужно подать ходатайство сегодня.

So there is no hidden subject in the same way English has it. The sentence is just structured impersonally.

That is a very normal feature of Russian:

• Нужно работать. = One needs to work / It is necessary to work.
• Нельзя курить. = Smoking is not allowed / One must not smoke.

Usually you add the person in the dative case.

Examples:

• Мне нужно подать ходатайство сегодня. = I need to submit the petition today.
• Вам нужно подать ходатайство сегодня. = You need to submit the petition today.
• Ему нужно подать ходатайство сегодня. = He needs to submit the petition today.

This is a very common pattern:

[dative person] + нужно + infinitive

So:

• мне = to me
• тебе = to you
• ему / ей = to him / her
• нам = to us
• вам = to you (plural/formal)
• им = to them

Even though the literal structure is something like to me it is necessary to..., the natural English translation is simply I need to...