В случае если таможенная декларация готова, таможенное оформление начнётся.

Yes. В случае если means in the event that or if in a more formal, bureaucratic, or written style.

• если = if
• в случае если = in the event that / if

So this sentence sounds official, which fits words like таможенная декларация and таможенное оформление.

In everyday speech, a Russian speaker would often just say:

Если таможенная декларация готова, таможенное оформление начнётся.

Случае is the prepositional singular of случай.

The expression is:

• в случае = in the case / in the event

After в in this meaning of location or circumstance, Russian uses the prepositional case:

• случай → в случае

This whole phrase в случае если functions like a conjunction meaning if / in the event that.

Because the sentence has two clauses:

1. В случае если таможенная декларация готова
2. таможенное оформление начнётся

The first clause gives the condition, and the second clause gives the result. In Russian, conditional subordinate clauses are separated by a comma, just as in English:

• If the customs declaration is ready, customs clearance will begin.

So the comma is required.

Готова is the short form of the adjective готовый (ready).

Russian often uses the short form of adjectives in statements like is ready, is necessary, is possible, etc.

Here:

• декларация is feminine singular
• so the short-form adjective must also be feminine singular:
  • masculine: готов
  • feminine: готова
  • neuter: готово
  • plural: готовы

So:

• таможенная декларация готова = the customs declaration is ready

The full form готовая would usually describe a noun directly, like готовая декларация = a ready/prepared declaration, not the declaration is ready.

Because it is the subject of the clause:

• таможенная декларация готова = the customs declaration is ready

In Russian, the subject of a sentence is normally in the nominative case.

Here both words are nominative feminine singular:

• таможенная — adjective, feminine singular nominative
• декларация — noun, feminine singular nominative

Because оформление is a neuter noun, so the adjective must also be neuter.

• таможенный = masculine
• таможенная = feminine
• таможенное = neuter

Since оформление is neuter singular, the correct form is:

• таможенное оформление

This means customs clearance or customs processing.

It is in the nominative case.

In the main clause:

• таможенное оформление начнётся

the subject is таможенное оформление, so it stays in the nominative.

This literally means:

• customs clearance will begin

Начнётся is the future tense of the perfective verb начаться (to begin, to start).

Because the sentence talks about a future event that will happen once the condition is met, Russian uses the future:

• начаться → начнётся = will begin

This is a common pattern:

• condition in the present: если ... готова
• result in the future: ... начнётся

Because the verb is начаться, not начать.

• начать = to begin/start something (transitive)
• начаться = to begin/start (intransitive, to begin on its own)

Here, таможенное оформление is itself the thing that begins, so Russian uses начаться:

• Оформление начнётся = The processing will begin

The -ся often marks verbs that work like to begin, to happen, to open, etc., where the subject undergoes the action rather than directly doing it to something else.

It is primarily if.

The sentence presents a condition:

• В случае если таможенная декларация готова, ...
• If the customs declaration is ready, ...

In context, English might sometimes translate this naturally as once or when if the condition is expected to be fulfilled, but grammatically Russian если still means if.

Yes. Russian word order is flexible, though some versions sound more natural or more formal than others.

The given sentence is perfectly natural in official style:

• В случае если таможенная декларация готова, таможенное оформление начнётся.

You could also say:

• Если таможенная декларация готова, таможенное оформление начнётся.
• Таможенное оформление начнётся, если таможенная декларация готова.

The meaning stays basically the same, but the emphasis changes slightly. Putting the condition first is very common in formal instructions and notices.

Because the condition is described as a present state, while the result is a future event.

• декларация готова = the declaration is ready
• оформление начнётся = the processing will begin

This is normal in both Russian and English:

• If the declaration is ready, customs clearance will begin.

Russian does not need a future form in the if clause here.

It is pronounced roughly nach-NYO-tsya.

The letter ё always carries stress, so in начнётся the stress is on ё:

• начнётся

This matters because е and ё are pronounced differently. In many printed texts, ё is sometimes replaced by е, and you may see начнется, but it still means the same word. For learners, keeping ё helps a lot with pronunciation and stress.

It is natural Russian, but it sounds formal and administrative.

That is because of expressions like:

• в случае если
• таможенная декларация
• таможенное оформление

This is the kind of wording you might see in official instructions, customs regulations, or government documents. In less formal speech, people would probably simplify it to:

• Если декларация готова, оформление начнётся.

or even something more conversational, depending on context.