mousikomisyo wo dasu mae ni, matigai wo syuuseisite okimasu.

Because 前に means before doing X, and when a verb comes before 前, you normally use the dictionary form of the verb.

So:

• 出す前に = before submitting / before handing in
• 食べる前に = before eating
• 寝る前に = before sleeping

By contrast, with 後で / 後に (after), Japanese often uses the past form:

• 出した後で = after submitting

So this sentence follows a very common pattern:

• Verb dictionary form + 前に = before doing
• Verb past form + 後で / 後に = after doing

Here, 前に means before in the time sense.

The phrase:

• 申込書を出す前に
  means
• before submitting the application form

Structurally, 前 is a noun meaning front / before, and に marks the time point.

So the sentence is divided like this:

• 申込書を出す前に = before submitting the application form
• 間違いを修正しておきます = I’ll correct the mistakes in advance

Yes, 出す has a basic meaning like to put out / send out / take out, but in Japanese it is also very commonly used for submitting or handing in documents.

So:

• レポートを出す = submit a report
• 宿題を出す = hand in homework
• 申込書を出す = submit an application form

This is a very natural use of 出す. English often uses a more specific verb like submit, while Japanese often uses broader everyday verbs in context.

申込書 means application form.

It breaks down like this:

• 申込（もうしこみ） = application / sign-up / request
• 書（しょ） = document / form / written paper

So 申込書 is a written form used to apply for something.

You may also see the related word:

• 申し込み = application, sign-up
• 申し込む = to apply

Because there are really two different verb phrases here, and each one has its own direct object.

1. 申込書を出す

   • object: 申込書
   • verb: 出す

2. 間違いを修正しておきます

   • object: 間違い
   • verb: 修正しておきます

So the full sentence contains:

• [申込書を出す] 前に
• 間違いを修正しておきます

The first を belongs to 出す, and the second を belongs to 修正する.

This is one of the most important points in the sentence.

• 修正します = I will correct them / I correct them
• 修正しておきます = I will correct them in advance / ahead of time / so they’ll be ready

The pattern 〜ておく adds the idea of doing something beforehand, often as preparation for a later event.

So here:

• 申込書を出す前に、間違いを修正します。
  = Before submitting the application form, I’ll correct the mistakes.

• 申込書を出す前に、間違いを修正しておきます。
  = Before submitting the application form, I’ll correct the mistakes in advance / beforehand.

The second one sounds more like preparation and planning.

〜ておく often means:

• do something in advance
• do something to prepare
• do something and leave it done

In this sentence, it suggests something like:

• I’ll make the corrections now so the form is ready to submit later.

So the speaker is not just correcting mistakes; they are doing it as a preparatory step.

This pattern is extremely common:

• 予約しておきます = I’ll make a reservation in advance.
• メモしておいてください = Please make a note of it beforehand.
• 確認しておきます = I’ll check it in advance.

Because しておきます comes from the て-form of する.

The verb is:

• 修正する = to correct / revise

Its て-form is:

• 修正して

Then add おきます:

• 修正しておきます

So this is the normal formation of 〜ておく:

• 食べる → 食べておく
• 読む → 読んでおく
• する → しておく

Since this sentence is polite, it becomes:

• 修正しておきます

In Japanese, the non-past form covers both present and future, depending on context.

So 修正しておきます can mean:

• I do it in advance
• I will do it in advance

In this sentence, because of before submitting the application form, the meaning is naturally future-oriented:

• Before I submit the application form, I’ll correct the mistakes beforehand.

This is completely normal in Japanese. The language does not require a separate future tense the way English often does.

Yes, it is natural, though it sounds a bit more formal or written than some alternatives.

• 間違い = mistake
• 修正する = correct / revise

So 間違いを修正する means to correct mistakes.

A more casual alternative would often be:

• 間違いを直す = fix/correct mistakes

The nuance is roughly:

• 修正する = more formal, often used for documents, text, data, applications, written work
• 直す = more everyday, broad, casual

Since this sentence is about an application form, 修正する fits very well.

Japanese often omits the subject when it is understood from context.

So this sentence does not explicitly say:

• I
• you
• we
• someone

But because the main verb is おきます in polite form, and because the sentence sounds like someone describing what they will do, it is very naturally understood as something like:

• I’ll correct the mistakes before submitting the application form.

In another context, it could refer to someone else, but without more information, English usually supplies I.

Japanese often puts the time condition or context first, and the main action later.

So:

• 申込書を出す前に = before submitting the application form
• 間違いを修正しておきます = I’ll correct the mistakes in advance

This is very natural Japanese word order:

• [When / before / if / because ...], [main action].

For example:

• 寝る前に、歯を磨きます。 = Before going to bed, I brush my teeth.
• 出かける前に、戸締まりを確認します。 = Before going out, I check the locks.

Yes. The comma is helpful, but it is not absolutely required.

So both are possible:

• 申込書を出す前に、間違いを修正しておきます。
• 申込書を出す前に間違いを修正しておきます。

The comma just makes the pause clearer and improves readability. In writing, Japanese punctuation is often somewhat flexible compared with English.

Normally, 前に is the standard form here.

• 出す前に = before submitting

Leaving out に is generally not the usual choice in this pattern for learners. In natural Japanese, 前に is what you should use.

So for practical purposes, it is best to remember:

• Verb dictionary form + 前に

Example:

• 帰る前に電話します。 = I’ll call before going home.

Yes, mostly in tone and style.

• 修正しておきます = I’ll revise/correct it in advance

  • slightly more formal
  • good for documents, written content, applications

• 直しておきます = I’ll fix/correct it in advance

  • more everyday and casual
  • very common in speech

Since this sentence is about an application form, 修正しておきます sounds especially appropriate because it matches the document-related situation well.