Learn Hardcore Korean: gyeoljereul wanryohaesseoyo.

결제: “payment” (a noun)
를: object marker (marks 결제 as the thing acted on)
완료했어요: past/present-perfect polite form of 완료하다 “to complete” So it’s literally: “(I) payment-OBJ completed.”

Who is the subject here?

It’s omitted and understood from context. By default, it often means “I.” To say it explicitly, use:

제가 결제를 완료했어요. (I completed the payment.) Use 제가 (subject marker) to emphasize that you are the one who did it.

Why is it 를 and not 을 after 결제?

을/를 is chosen by the noun’s final sound:

After a consonant: 을
After a vowel: 를 결제 ends in a vowel sound, so 결제를 is correct.

Can I drop the object particle 를?

Often yes in casual speech: 결제 완료했어요. Koreans frequently omit 을/를. In careful or formal writing, keep 를 to be clear: 결제를 완료했어요.

What politeness level is 했어요? When would I change it?

-어요/-아요 is polite informal (standard polite). Variants:

Casual: 완료했어
Formal/polite: 완료했습니다
Very formal/written/system message: 완료되었습니다 (passive; see below)

Active vs. passive: what’s the difference between 완료했어요 and 완료됐어요?

결제를 완료했어요: active; focuses on the doer (“I completed the payment”).
결제가 완료됐어요: passive; focuses on the result/state (“The payment has been completed”). System notifications typically use the passive: 결제가 완료되었습니다.

How is this different from just saying 결제했어요?

결제했어요 = “I paid” (simple and very common).
결제를 완료했어요 sounds a bit more formal/explicit about completion (common in app or service contexts). In everyday talk, 결제했어요 is usually enough.

Can I use 끝나다/끝내다 instead of 완료하다?

Yes, with nuance:

결제가 끝났어요 (intransitive): “The payment is finished.” (state/result)
결제를 끝냈어요 (transitive): “I finished the payment.” (more casual than 완료하다) 완료하다 sounds more formal/official than 끝내다.

I often see 결제 vs. 결재. What’s the difference?

결제 (決濟): payment/settlement of money.
결재 (決裁): approval/sign-off by a superior. They’re pronounced the same [결쩨], but mean different things. In this sentence, you need 결제 (payment).

How do I pronounce the whole sentence naturally?

결제 → [결쩨]
결제를 → [결쩨를]
완료 → [왈료] (ㄴ+ㄹ → ㄹㄹ assimilation)
했어요 → [해써요] Full sentence: [결쩨를 왈료해써요].

Why is 완료했어요 written together and not as 완료 했어요?

Because 완료하다 is a verb (noun + 하다 compounds into one verb). So you write 완료했어요 together. Don’t split it as 완료 했어요. By contrast, a status label like 결제 완료 (payment complete) is a noun phrase, so it’s written with a space.

How can I emphasize or contrast things?

Emphasize the doer: 제가 결제를 완료했어요.
Contrast the topic: 결제는 완료했어요 (I did finish the payment, but maybe not something else).
“Only” the payment: 결제만 완료했어요.

Is 결제가 완료되셨어요 okay? I’ve seen it in service talk.

It’s common in service speech, but standard grammar avoids adding honorific -시- to inanimate subjects like 결제. Prefer:

결제가 완료되었습니다. (standard formal)
If honoring the customer as the doer: 고객님께서 결제를 완료하셨습니다.

Does 했어요 mean simple past or present perfect?

Korean -았/었- covers both. 완료했어요 can be “completed” or “have completed.” Add adverbs for clarity:

방금/지금 막 완료했어요 = just completed
이미/벌써 완료했어요 = already completed

How do I say it in the future?

결제를 완료할게요: I will complete it (promise/volition to the listener).
결제를 완료할 거예요: I’m going to complete it (plan/intention/prediction).

How do I say I couldn’t/didn’t complete it?

Inability/failed attempt: 결제를 완료하지 못했어요.
Plain negation: 결제를 안 했어요 or 결제를 완료 안 했어요 (the former is more natural; for the verb 완료하다, use 못/지 않다: 완료하지 않았어요).

Are there near-synonyms to 결제, and when are they used?

결제: payment/settlement (e-commerce, cards, checkout).
지불: paying (formal/literary; “funds disbursement” feel).
계산: “check out/pay the bill” at restaurants/shops.
입금: deposit (into an account).
송금: remittance/transfer (sending money).
정산: settling accounts/reconciling after expenses.