seikyuubi wo kakuninsuru.

It is read:

• 請求日 = せいきゅうび
• を = o (written wo, but pronounced o here)
• 確認する = かくにんする

So the whole sentence is:

せいきゅうび を かくにんする。

In natural writing, it would usually appear without spaces:

請求日を確認する。

請求日 usually means the billing date or invoice date.

Breakdown:

• 請求 = claim, demand, bill, invoice
• 日 = day / date

So 請求日 is the date associated with issuing a bill or invoice.

Depending on context, it is usually not the same as the payment due date. A due date would more often be something like:

• 支払日 = payment date
• 支払期限 = payment deadline

を marks the direct object of the verb.

In this sentence, the thing being checked/confirmed is 請求日. So:

• 請求日 = the billing date
• を = object marker
• 確認する = to check / confirm

So the structure is:

[thing being checked] + を + 確認する

In other words: check the billing date.

Japanese often leaves out the subject when it is obvious from context.

So 請求日を確認する。 could mean:

• I check the billing date
• You should check the billing date
• Check the billing date
• To check the billing date

Which one it means depends on the situation.

This is very normal in Japanese. English usually needs an explicit subject, but Japanese often does not.

The plain form 確認する is often used in:

• dictionary entries
• headings
• instructions in manuals
• labels in interfaces
• notes or memo-style writing
• short procedural steps

So 請求日を確認する。 can sound like a simple instruction or action item: Check the billing date.

If you wanted a polite sentence, you could say:

• 請求日を確認します。 = I will check / check the billing date.
• 請求日を確認してください。 = Please check the billing date.

確認する is more specific than 見る.

• 見る = to look at / to see
• 確認する = to confirm, verify, make sure, check carefully

So 請求日を見る would simply mean look at the billing date.

But 請求日を確認する means more like:

• check what the billing date is
• verify that the billing date is correct
• make sure of the billing date

So 確認する has a stronger sense of verifying or making sure.

Grammatically, it is a noun + する verb.

• 確認 = confirmation, checking
• する = to do

Together, 確認する means to confirm / to check.

This is a very common pattern in Japanese, especially with words of Chinese origin:

• 勉強する = to study
• 電話する = to call
• 説明する = to explain
• 確認する = to confirm

So even though it functions as a verb, it is built from a noun plus する.

The kanji 日 has several common readings, and the reading often depends on the compound.

In 請求日, it is read び, so:

• 請求日 = せいきゅうび

This is something you often just have to learn with the word. Common readings of 日 include:

• ひ as a standalone word meaning day
• にち in many compounds
• び in some compounds, especially dates or named days

So this is not unusual; it is just the standard reading for this compound.

Yes. Japanese usually puts the verb at the end.

English:

• check the billing date

Japanese:

• billing date + object marker + check
• 請求日を確認する

So the basic order here is:

object + を + verb

This is very common in Japanese.

Not usually. In normal Japanese writing, you would typically write:

請求日を確認する。

Spaces are often added in learning materials to make the sentence easier to read, but standard Japanese does not normally separate words with spaces the way English does.

Yes. 確認する can be translated in several similar ways depending on context:

• check
• confirm
• verify
• make sure of

So 請求日を確認する。 could naturally be understood as:

• check the billing date
• confirm the invoice date
• verify the billing date

The exact English wording depends on the situation, but the Japanese nuance is basically make sure what the billing date is / that it is correct.