Learn Hardcore Korean: hyeongeumeul naemyeon geoseureumdoneul kkok hwaginhaseyo. - When you pay in cash, be sure to check the change.

The suffix -면 attaches to verb stems to form “if/when” clauses. You take the verb 내다 (“to pay”), drop -다, add -면 → 내면. You can attach -면 to most verbs: 가다 → 가면 (“if/when you go”), 보다 → 보면 (“if/when you see”).

What exactly is 거스름돈?

거스름돈 is a noun meaning “change” (the money you get back after paying). It literally combines 거슬리다 (“to be given back”) with -돈 (“money”), so “money given back.”

Why is there an object marker -을 in 거스름돈을 확인하세요?

In Korean, transitive verbs like 확인하다 (“to check”) take an object, marked by -을/를. Since 거스름돈 ends with a consonant, you use -을 → 거스름돈을 확인하세요.

What nuance does 꼭 add to 거스름돈을 꼭 확인하세요?

꼭 adds emphasis, meaning “definitely,” “without fail,” or “be sure to.” It stresses that checking your change is important.

Is 확인하세요 polite, and could I say it differently?

확인하세요 is a standard polite (존댓말) imperative form of 확인하다. You could also say 확인해 주세요 (“please check”) for a softer request, or use the casual 확인해 with friends/family.

Can I reorder the sentence and still sound natural?

Yes. You could say 현금을 내면 꼭 거스름돈을 확인하세요 or 거스름돈을 꼭 확인하세요 현금을 내면 (the second is poetic/uncommon). The most natural is keeping the condition first, then the instruction.

Why not just say 거스름돈 확인하세요 without 현금을 내면?

If you omit 현금을 내면, it becomes a general instruction “Check your change,” but you lose the context “when paying cash.” The conditional clause clarifies that the advice applies in that situation.