Страхователь оплатил страховую премию.

Because страховую премию is the direct object of the verb оплатил.

The dictionary form is:

• страховая премия = nominative singular

But after оплатить you need the accusative:

• страховую премию = accusative singular

For feminine singular words, this change is very common:

• adjective -ая → -ую
• noun -ия → -ию

So:

• страховая премия → страховую премию

In the past tense, Russian verbs agree with the subject in gender and number.

The subject here is страхователь, which is grammatically masculine singular, so the verb is:

• оплатил = masculine singular past

Compare:

• страхователь оплатил = a male policyholder paid
• страховательница оплатила = a female policyholder paid
• страхователи оплатили = policyholders paid

Оплатил is perfective, so it presents the payment as a completed action.

That fits a simple statement of fact: the payment was made.

Compare:

• оплатил = paid, completed the payment
• платил = was paying / used to pay / paid repeatedly
• оплачивал = was paying / paid on a repeated or ongoing basis

So this sentence is about one completed event, which is why оплатил is natural.

Because оплатить normally takes a direct object in the accusative:

• оплатить что?
• оплатить страховую премию

This is a very common Russian pattern with оплатить: you directly name the thing being paid.

Compare different payment verbs:

• оплатить страховую премию = to pay the insurance premium
• заплатить за страховку = to pay for the insurance
• заплатить страховой компании = to pay the insurance company

So the structure depends on the verb.

They are two different roles:

• страхователь = the policyholder, the person or company that takes out the insurance
• страховщик = the insurer, the insurance company

This distinction is important in legal and insurance Russian.

Also, страхователь is built from:

• страховать = to insure
• suffix -тель = a person who does something

So страхователь literally means something like the insuring party.

Not exactly.

• страховая премия is the insurance premium, meaning the payment due under the insurance contract
• страховка is a more everyday word that usually means insurance, insurance policy, or coverage

In casual speech, people may say things like оплатить страховку, but in formal or legal language страховая премия is more precise.

Yes. It sounds fairly official, businesslike, or legal.

Words like страхователь and страховая премия belong to insurance terminology.

In everyday conversation, a Russian speaker might say something simpler, such as:

• Он заплатил за страховку.
• Клиент оплатил страховку.

So the original sentence is correct, but it sounds more like something from a contract, report, or official document.

Yes. Russian word order is flexible.

The sentence as given:

• Страхователь оплатил страховую премию.

is the most neutral order: subject + verb + object.

You could also say:

• Страховую премию оплатил страхователь.

That version puts more focus on страховую премию or creates a contrast, as if answering Who paid the premium?

So the grammar stays the same, but the emphasis changes.

The stress is:

• страховáтель
• оплати́л
• страхову́ю
• пре́мию

So the full sentence is:

• страховáтель оплати́л страхову́ю пре́мию

A couple of pronunciation notes:

• unstressed о often sounds closer to a
• the ль in -тель is soft
• ю in премию is pronounced like yu

Because Russian has no articles.

Russian does not have direct equivalents of English a/an and the. Whether English needs a policyholder, the policyholder, an insurance premium, or the insurance premium depends on context.

Russian expresses definiteness in other ways, such as:

• context
• word order
• intonation
• the situation being discussed

So the Russian sentence can be fully natural without any article words at all.