Obligation with -아/어야 하다 and 되다 in Korean

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concept: ko-a2-obligation-ya-hada lang: ko ui: en title: Obligation in Korean: -아/어야 하다 and 되다 description: >- Learn how to say must, have to, do not have to, and must not in Korean with -아/어야 하다/되다, -아/어도 되다, and -(으)면 안 되다. generation: article: version: native-ui-reference-v3.1 model: openai-codex/gpt-5.6-sol at: 2026-07-11T15:31:58Z reviews: spell-check: status: clean at: 2026-07-11T15:31:58Z score: 0 score-english: null score-coverage: null criteria: v7 language-mixing: status: clean at: 2026-07-11T15:35:21Z criteria: v2

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In Brief

Attach -아/어야 하다 or -아/어야 되다 to a verb to say that someone must or has to do something: 가야 해요 and 가야 돼요 both mean “I/you have to go,” depending on context. Keep two different negatives separate: -아/어도 되다 means “do not have to,” while -(으)면 안 되다 means “must not.”

Overview

Korean does not need a separate word corresponding exactly to English must. Instead, it joins an ending to the verb that describes the necessary action. The two everyday patterns are -아/어야 하다 and -아/어야 되다. They are very close in meaning, and both can express a rule, a practical necessity, a duty, or something the speaker considers necessary.

This is a core A2 pattern. It builds directly on the polite -아/어요 forms: if you can produce 가요, 먹어요, and 해요, the first part of 가야 해요, 먹어야 해요, and 해야 해요 will feel familiar. Korean often leaves the subject unstated, so 가야 해요 can mean “I have to go,” “you have to go,” or “they have to go.” The situation tells you who has the obligation.

English learners need to pay special attention to the negative forms. English must not prohibits an action, but do not have to removes the necessity. Korean makes the same distinction with two completely different structures. Mixing them up can turn “You need not come” into “You may not come.”

How It Works

The beginner rule

Start with the verb stem (the dictionary form without -다), add -아야 or -어야, and finish with 하다 or 되다.

Pattern	Korean example	Meaning
verb stem + -아/어야 하다	가야 하다	to have to go
verb stem + -아/어야 되다	가야 되다	to have to go

In polite conversation, conjugate the final verb:

• 하다 → 해요: 가야 해요
• 되다 → 돼요: 가야 돼요

The spelling 돼요 is the contraction of 되어요. 되요 is not the standard spelling.

Choosing -아야 or -어야

The vowel choice follows the same broad pattern as -아/어요.

Stem type	Ending	Dictionary form	Obligation form
Last vowel is ㅏ or ㅗ	-아야	가다	가야 해요
Other vowel	-어야	먹다	먹어야 해요
하다 verb	해야	공부하다	공부해야 해요

Normal contractions and irregular conjugations occur before -야 just as they do before -아/어요:

Dictionary form	Intermediate form	With obligation	Meaning
오다	와야	와야 해요	have to come
보다	봐야	봐야 해요	have to see/watch
배우다	배워야	배워야 해요	have to learn
쓰다	써야	써야 해요	have to write/use
듣다	들어야	들어야 해요	have to listen
돕다	도와야	도와야 해요	have to help
준비하다	준비해야	준비해야 해요	have to prepare

Do not attach the pattern to the full dictionary form: begin with 먹- from 먹다, not with 먹다 itself.

하다 or 되다?

In this construction, -아/어야 하다 and -아/어야 되다 are usually interchangeable. Both are natural, and neither requires a special English translation.

Korean	English	Note
이제 출발해야 해요.	We have to leave now.	하다 version
이제 출발해야 돼요.	We have to leave now.	되다 version; very common in speech

You may encounter explanations that assign a firm difference such as “personal duty” versus “external necessity.” Context can create such shades of meaning, but everyday usage does not maintain a reliable one-to-one contrast. At A2, treat the two forms as equivalent and learn both.

Saying “do not have to”

To remove an obligation, use -아/어도 되다, literally presenting the action as acceptable even if it happens—or use a negative action before that pattern:

• 안 + verb + -아/어도 되다: 안 가도 돼요. — “You do not have to go.”
• verb stem + -지 않아도 되다: 가지 않아도 돼요. — “You do not have to go.”

The short 안 pattern is especially common in conversation. The -지 않아도 되다 pattern is useful when the verb phrase is longer or when you want the negative structure to be completely clear.

Korean	English	Note
오늘은 숙제 안 해도 돼요.	You do not have to do homework today.	Conversational short negation
오늘은 숙제를 하지 않아도 돼요.	You do not have to do homework today.	Longer negative form

This pattern removes necessity; it does not forbid the action. 안 와도 돼요 means that coming is optional, not that coming is prohibited.

Saying “must not”

For a prohibition, use -(으)면 안 되다 after the action that is forbidden. The ending -(으)면 introduces a condition (an “if/when” clause), so the construction can be understood as “if you do it, it is not acceptable.”

Stem ending	Form	Example	Meaning
Vowel or ㄹ	-면 안 되다	가면 안 돼요	must not go
Other consonant	-으면 안 되다	먹으면 안 돼요	must not eat
하다	하면 안 되다	운전하면 안 돼요	must not drive

This is not the negative of -아/어야 하다 formed word by word. Learn it as its own prohibition pattern.

Tense, politeness, and sentence endings

The final 하다 or 되다 carries the tense and speech level. The obligation part normally stays unchanged.

Form	Korean	Typical meaning
Polite everyday	가야 해요 / 가야 돼요	have to go
Formal polite	가야 합니다 / 가야 됩니다	have to go
Casual	가야 해 / 가야 돼	have to go
Past	가야 했어요 / 가야 됐어요	had to go
Question	가야 해요? / 가야 돼요?	Do I/you have to go?

English often uses the word order “Do I have to...?” Korean generally uses the same obligation form and signals a question through the ending and intonation: 지금 가야 해요?

Examples in Context

Korean	English	Note
가야 해요.	I have to go.	The subject is understood from context.
공부해야 돼요.	I have to study.	하다 becomes 해야.
내일까지 보고서를 써야 해요.	I have to write the report by tomorrow.	A deadline creates the necessity.
약을 하루에 두 번 먹어야 돼요.	You have to take the medicine twice a day.	A practical or medical requirement
회의에 꼭 참석해야 합니다.	You must attend the meeting.	Formal polite style; 꼭 stresses necessity.
몇 시까지 와야 해요?	What time do I have to come by?	Asking for a requirement
여기에서 신발을 벗어야 돼요?	Do I have to take off my shoes here?	Asking about a local custom or rule
어제 늦게까지 일해야 했어요.	I had to work late yesterday.	Past necessity
안 가도 돼요.	You do not have to go.	Going is optional.
예약하지 않아도 돼요.	You do not have to make a reservation.	Long negative form
이 칸은 작성하지 않아도 됩니다.	You do not need to fill in this box.	Formal instructions
여기서 담배 피우면 안 돼요.	You must not smoke here.	Prohibition
수업 중에 전화하면 안 돼요.	You must not make calls during class.	A rule
이 문을 열면 안 됩니다.	This door must not be opened.	Formal prohibition
비밀번호를 다른 사람에게 말하면 안 돼요.	You must not tell anyone else your password.	A warning

Notice that several English subjects are supplied in translation even though Korean states none. Avoid automatically adding 저는 or 당신은 to every sentence. Korean usually relies on context, and 당신 is not a neutral everyday equivalent of English you.

Common Mistakes

Confusing “do not have to” with “must not”

• Wrong for “You do not have to come”: 오면 안 돼요.
• Right: 안 와도 돼요. / 오지 않아도 돼요.
• Why: 오면 안 돼요 forbids coming. 안 와도 돼요 says that not coming is acceptable, so attendance is optional.

Adding -야 directly to an unchanged stem

• Wrong: 먹야 해요.
• Right: 먹어야 해요.
• Why: Add -아야/-어야 according to the same vowel pattern used in -아/어요. A consonant-ending stem such as 먹- needs -어야.

Keeping 하다 unchanged

• Wrong: 공부하야 돼요.
• Right: 공부해야 돼요.
• Why: 하다 + -아/어야 contracts to 해야.

Writing 되요

• Wrong: 가야 되요.
• Right: 가야 돼요.
• Why: 되어요 contracts to 돼요. The uncontracted 되어요 is possible but uncommon in ordinary conversation.

Negating the wrong part

• Wrong for “I do not have to buy it”: 사야 안 해요.
• Right: 안 사도 돼요. / 사지 않아도 돼요.
• Why: Korean normally expresses absence of necessity with the permission-shaped pattern negative action + -아/어도 되다, not by placing 안 before the final 하다.

Translating English “you” too literally

• Awkward in many contexts: 당신은 지금 가야 해요.
• Natural when the person is obvious: 지금 가야 해요.
• Why: Korean commonly omits an understood subject. Names, titles, or kinship terms are often used when the listener must be identified; 당신 has restricted and context-sensitive uses.

Usage Notes

In everyday polite speech, both 해야 해요 and 해야 돼요 are extremely common. The contractions 해야 돼요 and casual 해야 돼 are standard conversational forms, not careless grammar. In formal announcements, workplace instructions, and written rules, 해야 합니다/해야 됩니다 and -(으)면 안 됩니다 are common.

The construction itself can sound neutral, but telling another person what they “have to” do may feel direct. Korean speakers often soften advice with context, a reason, or a less forceful ending: 내일 일찍 일어나야 하니까 이제 자는 게 좋겠어요 (“Since you have to get up early tomorrow, it would be good to sleep now”). When stating an impersonal rule, a formal style can make the requirement sound institutional rather than personal.

Words such as 꼭 (“definitely; without fail”) and 반드시 (“necessarily; without exception”) strengthen the obligation. 꼭 와야 해요 means “You really must come.” 반드시 is frequent in firm instructions and formal writing. Neither word is required for the basic grammar.

Beyond the Basics / Advanced Use

You do not need to master these points at A2, but you will meet them often.

-아/어야겠다: realizing what must be done

Attach -겠다 to the final verb when the speaker reaches a decision or recognizes a necessity:

• 이제 가야겠어요. — “I should get going now.”
• 운동을 더 해야겠어요. — “I should exercise more.”

This often sounds like a personal resolution rather than an externally imposed rule.

-아/어야지: resolve, expectation, or reminder

In conversation, -아/어야지(요) can express the speaker’s resolve or an expectation about what someone ought to do:

• 내일부터 일찍 자야지. — “I’m going to start going to bed early tomorrow.”
• 약속은 지켜야지요. — “You should keep a promise, of course.”

Tone and context matter. Directed at someone else, this can sound like a reminder, criticism, or moral expectation.

-았/었어야 하다: something should have happened

A past marker inside the first part commonly expresses an unfulfilled past duty or regret:

• 더 일찍 출발했어야 했어요. — “We should have left earlier.”
• 그때 사실을 말했어야 해요. — “I should have told the truth then.”

This differs from ordinary past necessity. 출발해야 했어요 means “I had to leave”; 출발했어야 했어요 usually means “I should have left,” often implying that I did not.

Written and emphatic variants

You may see -아/어야 한다 in neutral written prose, articles, rules, and definitions. The ending -아/어야만 하다, with 만, emphasizes that the action is indispensable:

• 신분증을 반드시 가져와야 한다. — “You must bring identification.”
• 회원만 신청해야 하는 것은 아닙니다. — “It is not the case that only members must apply.”

The fuller form -아/어야만 하다 is stronger than the ordinary conversational pattern. -아/어야 can also connect directly to a following result, as in 직접 봐야 알 수 있어요 (“You can know only if you see it yourself”). Here it expresses a necessary condition, not simply a social duty.

Practice Tips

1. Build four-way sets. Take one verb and say obligation, past obligation, no obligation, and prohibition: 가야 해요 → 가야 했어요 → 안 가도 돼요 → 가면 안 돼요. This prevents the two negative meanings from merging in your memory.
2. Reuse your -아/어요 knowledge. Make a list such as 와요, 먹어요, 배워요, 들어요, 해요, then replace the final 요 with 야 해요 where appropriate: 와야 해요, 먹어야 해요, 배워야 해요, 들어야 해요, 해야 해요.
3. Listen for the final verb. In natural speech, identify whether you hear 해요, 돼요, 했어요, or 됐어요. That final element tells you the speech level and time, while the preceding -아/어야 carries the idea of necessity.

Related Concepts

• Prerequisite: Polite Ending -아/어요 — supplies the vowel patterns and everyday polite endings used throughout this construction.
• Next step: Permission -아/어도 되다 — develops the permission pattern that also appears in “do not have to.”