Learn Hardcore Korean: neutge chekeuaushamyeon chuga yogeumi bugwadwaeyo. - If you check out late, an additional fee is imposed.

The ending -(으)면 is a conditional: “if/when.” In rule-like statements, it often means “whenever.” Here it reads as “If/When you check out late, …”

Why is it 늦게 and not 늦은?

늦게 is an adverb that modifies a verb: 늦게 체크아웃하다 = “to check out late.”
늦은 is an adjective that modifies a noun: 늦은 체크아웃 = “a late check-out” (as a noun phrase). Both are fine depending on structure:
늦게 체크아웃하면 …
늦은 체크아웃을 하면 …

Why use the passive 부과돼요 instead of the active 부과해요?

Korean often uses the passive to state general rules without naming an agent.

Passive (rule-like, agentless): 추가 요금이 부과돼요. = “An extra fee is imposed.”
Active (agent stated or implied): 호텔에서 추가 요금을 부과해요. = “The hotel imposes an extra fee.”
Both are correct; the passive sounds more neutral and sign-like.

Is 부과돼요 the correct spelling? Why not 부과되요?

Yes, 부과돼요 is correct. It comes from 부과되어요 → contracted to 부과돼요.

Dictionary form: 부과되다
Polite present (full): 부과되어요
Polite present (contracted, most common): 부과돼요
Formal: 부과됩니다
Note: 부과되요 is a common misspelling.

How do you pronounce this sentence naturally?

체크아웃하면 is pronounced close to [체크아우타면] because ㅅ(“웃”) + ㅎ(“하”) tends to sound like ㅌ.
늦게 sounds like [늑께] due to tensification.
돼요 in 부과돼요 sounds like [dwe-yo], not [de-yo].
Put together, a natural flow is roughly: [늑께 체크아우타면 추가 요금이 부과돼요].

Why 요금이 and not 요금은?

요금이 marks “extra fee” as the grammatical subject of the passive verb (부과돼요).
요금은 would topicalize it: “As for the extra fee, it is imposed (in that case).”
Both can be used, but 요금이 is the default in a neutral statement of fact.

Can I say 추가 비용이 부과돼요?

It’s better to use 부과되다 with items like 요금/세금/벌금/과태료. For 비용, more natural choices are:

비용이 청구돼요 (is billed/charged)
추가 비용이 발생해요 (additional costs arise)
비용이 추가돼요 (costs are added)
So prefer 추가 요금이 부과돼요 here.

What are other natural ways to express the same idea?

Polite formal (signage): 늦게 체크아웃하시면 추가 요금이 부과됩니다.
Obligation focus: 늦게 체크아웃하시면 추가 요금을 내셔야 해요.
Colloquial verb: 체크아웃이 늦으면 추가 요금이 붙어요.
Billing focus: 늦게 체크아웃하시면 추가 요금이 청구됩니다.
More explicit: 정해진 시간 이후에 체크아웃하시면 추가 요금이 부과됩니다.

Is 체크아웃하다 natural, or should I use something like 퇴실하다 or 나가다?

체크아웃하다 is perfectly natural and widely used in hotels.

퇴실하다 is more formal/literary (used in notices or for rooms).
나가다 just means “to go out/leave” and is too general on its own.

Can I say 체크아웃을 늦게 하면 instead of 늦게 체크아웃하면?

Yes. Both are idiomatic:

늦게 체크아웃하면 … (adverb modifying the verb directly)
체크아웃을 늦게 하면 … (noun + object marker + 하다)
The nuance difference is minimal; choose whichever flows better in context.

Why not 추가 요금을? Isn’t it the object of “impose”?

In the passive construction, 추가 요금이 is the subject of 부과돼요 (“is imposed”).
If you switch to active voice, you would use the object marker:

Active: 호텔에서 추가 요금을 부과해요.
Passive: 추가 요금이 부과돼요.

What politeness level is this? Would it appear on a sign?

…부과돼요 is the standard polite style for conversation.
On signs/notices, you’ll usually see the formal: …부과됩니다.
Even more formal instructions might use …하시기 바랍니다 or …해 주시기 바랍니다 in surrounding text.

What exactly does 부과 mean, and what does it collocate with?

부과(하다/되다) means “to levy/impose” (officially add a charge). It commonly goes with:

세금 (tax), 요금 (fee), 벌금 (fine), 과태료 (penalty), 보험료 (premium).
It sounds more formal/administrative than everyday “charge” words.

How can I soften the statement so it sounds less absolute?

Use possibility or hedging:

늦게 체크아웃하면 추가 요금이 부과될 수 있어요. (may be charged)
사정에 따라 추가 요금이 부과될 수 있습니다. (depending on circumstances)
경우에 따라 is another common hedge.

Why present tense 부과돼요 instead of future like 부과될 거예요?

Korean often states rules and habitual outcomes in the simple present.

…부과돼요 = general rule: “(it) is imposed (in that case).”
…부과될 거예요 emphasizes a specific prediction about the future event; it can sound less like a rule and more like a forecast.

Should it be 추가 요금 or 추가요금? And what about spacing with 체크아웃?

You’ll see both 추가 요금 and 추가요금; the compound form is common in practice, while spacing it (추가 요금) is also acceptable. Style guides vary; both are widely used.
As a verb, 체크아웃하다/체크아웃하면 is written solid. If you use it as a noun + 하다, write: 체크아웃을 하면.