nizyuuseikyuu ga aru.

It is read:

にじゅうせいきゅう が ある
nijū seikyū ga aru

• 二重 = にじゅう
• 請求 = せいきゅう
• が = ga
• ある = aru

In normal Japanese writing, you would usually write it without spaces: 二重請求がある.

二重請求 is a noun meaning a duplicate charge / double billing / duplicate claim, depending on context.

It is made of:

• 二重 = double, duplicated
• 請求 = billing, charge, claim, invoice demand

So together, 二重請求 refers to the situation where someone is billed twice or charged twice.

が marks what exists in this sentence.

The pattern is:

[thing] が ある = there is / there exists [thing]

So:

二重請求がある = There is a duplicate charge / A duplicate charge exists

If you used は, it would sound more like you are introducing 二重請求 as the topic and then saying something about it. With がある, the sentence is simply pointing out the existence of the duplicate charge.

Compare:

• 二重請求がある。 = There is a duplicate charge.
• 二重請求はある。 = As for duplicate charges, they do occur / there is one.
  This could sound contrastive depending on context.

ある is used for:

• inanimate objects
• abstract things
• events, situations, problems

いる is used for living beings that are animate, especially people and animals.

A duplicate charge is not a person or animal, so Japanese uses ある.

This is very common with abstract nouns:

• 問題がある = There is a problem.
• 理由がある = There is a reason.
• ミスがある = There is a mistake.
• 二重請求がある = There is a duplicate charge.

Yes. It is a complete sentence.

Japanese often uses very short sentences, especially in:

• customer service notes
• warnings
• system messages
• reports
• headlines
• casual conversation when the context is already clear

So 二重請求がある。 is perfectly possible as a standalone sentence, especially when someone is simply stating the issue.

In English, you might expect something longer like There appears to be a duplicate charge, but Japanese often leaves that extra framing out.

Japanese does not have articles like a, an, or the.

So 二重請求がある could mean:

• There is a duplicate charge
• There is the duplicate charge
• There are duplicate charges
  depending on context, though singular is the most natural reading here

The exact English choice depends on the situation, not on a special word in the Japanese sentence.

Yes. 請求 is a suru-noun, which means it can function as a noun or combine with する to make a verb.

• 請求 = a claim / a bill / charging
• 請求する = to claim / to bill / to charge

But in 二重請求がある, the whole expression 二重請求 is being used as a noun: a duplicate charge / double billing.

So this sentence is not saying someone charges twice. It is saying a duplicate charge exists.

It depends on the situation.

• 二重請求がある = plain form
• 二重請求があります = polite form

Use ある in:

• casual speech
• internal notes
• informal writing
• dictionary-style examples

Use あります in:

• speaking to customers
• workplace politeness
• formal explanations

For example:

• この明細には二重請求があります。 = There is a duplicate charge on this statement.

So the sentence you were given is natural, but it is in the plain style.

Japanese often omits information that is understood from context.

Possible omitted ideas could be:

• この請求書に = on this invoice
• カード明細に = on the card statement
• 問題として = as a problem
• どうやら = apparently

So in a real situation, 二重請求がある might mean something like:

• There is a duplicate charge on this bill.
• Apparently, there’s been double billing.
• A duplicate charge exists.

The sentence is short because Japanese often lets context do the work.

Yes, very easily.

Because 二重請求 is a problem, 二重請求がある often sounds like:

• reporting an issue
• pointing out an error
• warning someone
• noting a discrepancy

Depending on tone and context, it could be neutral, but in many real-life situations it carries the sense that something is wrong.

Here are the common forms:

• 二重請求がある。 = There is a duplicate charge.
• 二重請求がない。 = There is no duplicate charge.
• 二重請求があった。 = There was a duplicate charge.
• 二重請求がなかった。 = There was no duplicate charge.

Polite versions:

• 二重請求があります。
• 二重請求はありません。
• 二重請求がありました。
• 二重請求はありませんでした。

Notice that in negative polite sentences, は often appears naturally: ありません patterns often use は for contrast or topic marking.

Grammatically, it is more like:

There is double billing
or
A duplicate charge exists

It does not directly say who was charged.

If you want to say I was charged twice, Japanese would usually express that more specifically, for example with a sentence mentioning 私, カード, 料金, or a passive/affected expression.

So this sentence focuses on the existence of the billing problem, not on the person affected.