In short

합쇼체 is the crisp, formal register you hear in news broadcasts, announcements, presentations, the military, job interviews and polished service speech. Its statement ending is -습니다 after a 받침 and -ㅂ니다 after a vowel. It is not more polite than 해요체 - it is more formal and more distant, so 해요체 stays your everyday default and you switch into 합쇼체 only when the situation is public or ceremonial.

The rule

Step 1 - The declarative: -습니다 vs -ㅂ니다

The choice is decided by the 받침 of the verb or adjective stem, exactly like every other Korean allomorph pair.

Consonant-final (받침) stem + -습니다 / vowel-final stem + -ㅂ니다

• 먹다 -> stem 먹- (받침) -> 먹습니다 (meokseumnida, eats)
• 가다 -> stem 가- (vowel) -> 갑니다 (gamnida, goes)
• 하다 -> stem 하- (vowel) -> 합니다 (hamnida, does)

Note the pronunciation: the ㅂ of -ㅂ니다 meets the following ㄴ and is read as ㅁ, so 갑니다 is gamnida and 합니다 is hamnida - never gapnida or hapnida.

Step 2 - ㄹ-stems drop the ㄹ before -ㅂ니다

A stem that ends in ㄹ counts as vowel-like here and takes -ㅂ니다, but the ㄹ falls out first (the same ㄹ-deletion you met in lesson 17).

• 살다 -> 삽니다 (samnida, lives)
• 만들다 -> 만듭니다 (mandeumnida, makes)
• 알다 -> 압니다 (amnida, knows)

Step 3 - The four sentence endings

합쇼체 marks statement, question, command and suggestion with four different endings - unlike 해요체, where one form does all four jobs and only intonation separates them.

• Statement: -습니다 / -ㅂ니다 -> 갑니다, 먹습니다
• Question: -습니까? / -ㅂ니까? -> 갑니까? (gamnikka?), 먹습니까? (meokseumnikka?)
• Command: -(으)십시오 (built on the honorific -(으)시-) -> 가십시오 (gasipsio), 앉으십시오 (anjeusipsio, please sit). The negative command is -지 마십시오 - the -지 마세요 of lesson 21 with 말- taking -십시오 and dropping its ㄹ before the ㅅ, the same ㄹ-deletion as in Step 2: 찍지 마십시오 (jjikji masipsio, please do not take photos)
• Suggestion: -(으)ㅂ시다 -> 갑시다 (gapsida, let’s go), 먹읍시다 (meogeupsida, let’s eat)

You cannot make a question by adding ”?” to a statement: *갑니다? is wrong; the formal question has its own ending, 갑니까?

Step 4 - Tense, intention and honorifics stack, then -습니다 closes

The past -았/었- and the intention/conjecture marker -겠- both end in a ㅆ 받침, so after them the ending is always -습니다:

• -았/었- + -습니다: 가다 -> 갔습니다 (gatseumnida, went); 하다 -> 했습니다 (haetseumnida, did)
• -겠- + -습니다: 오다 -> 오겠습니다 (ogetseumnida, I will come); 알겠습니다 (algetseumnida, understood)

Subject honorification is a separate axis (lesson 22) and combines freely: -(으)시- + -ㅂ니다 -> -(으)십니다 and -(으)셨- + -습니다 -> -(으)셨습니다.

• 오다 -> 오십니다 (osimnida, [someone respected] comes)
• 오다 -> 오셨습니다 (osyeotseumnida, [someone respected] came)

Step 5 - The copula is always 입니다 / 아닙니다

Unlike 해요체’s 이에요/예요, the formal copula does not change with the noun’s 받침. It attaches to the vowel-final copula stem 이-, so it is always 입니다:

Noun + 입니다 (regardless of 받침) - 학생입니다 (haksaengimnida, is a student), 의사입니다 (uisaimnida, is a doctor). The negative is 아닙니다 (animnida, is not), following 이/가: 학생이 아닙니다.

Step 6 - Where it lives, and where 해요체 stays

Reach for 합쇼체 in public, one-to-many or hierarchical settings: 뉴스 (news), 발표 (presentations), 안내 방송 (announcements), 군대 (the military), 면접 (job interviews) and 서비스업 (service work - “어서 오십시오”). In ordinary conversation - shops, colleagues, friends, teachers - 해요체 is warmer and remains the default. A few frozen 합쇼체 expressions are used by everyone regardless of register: 감사합니다 (gamsahamnida, thank you), 안녕하십니까 (annyeonghasimnikka, hello - formal), 실례합니다 (sillyehamnida, excuse me), 알겠습니다 (algetseumnida, got it, understood).

Do not mix levels in one stretch of speech, and match the pronoun: 저는 … 합니다, never *저는 … 해.

Forms & patterns

The declarative allomorph, chosen by the stem:

The four sentence types (vowel-stem / 받침-stem):

Note that -(으)십시오 already contains the honorific -(으)시-, so for the verbs that have a suppletive honorific stem (lesson 22) you use that stem rather than the mechanical form: 드십시오 (deusipsio, please eat) is what is actually said, not 먹으십시오, and 주무십시오 (jumusipsio, please sleep), not 자십시오.

Tense, honorific and copula stacking:

해요체 <-> 합쇼체 conversion drill:

Examples

Common mistakes

• 가습니다. (Gaseumnida.) -> 갑니다. (Gamnida.) - A vowel-final stem takes -ㅂ니다, not -습니다. -습니다 is only for stems that end in a 받침.
• 살습니다. (Salseumnida.) -> 삽니다. (Samnida.) - A ㄹ-stem drops its ㄹ and takes -ㅂ니다. The same goes for 만듭니다, 압니다, 팝니다.
• 갑니다? (Gamnida?) -> 갑니까? (Gamnikka?) - You cannot turn a statement into a question with just a question mark. The formal question has its own ending, -ㅂ니까/-습니까.
• 학생습니다. (Haksaengseumnida.) -> 학생입니다. (Haksaengimnida.) - The copula stem 이- never disappears. After any noun the formal copula is always 입니다, whatever the 받침.
• 저는 회의에 참석하십니다. (Jeoneun hoeuie chamseokhasimnida.) -> 저는 회의에 참석합니다. (Jeoneun hoeuie chamseokhamnida.) - The honorific -(으)시- honours someone else, never yourself. Drop it when the subject is 저.

Tips

• -ㅂ니다 is read “mnida”. The single most audible beginner error is pronouncing the letters (hap-nida); Koreans always say hamnida, gamnida, imnida. Train the ear before the eye.
• Formality is not politeness. 합쇼체 and 해요체 are equally respectful of the listener; 합쇼체 is simply more formal and impersonal. Using it with a friend sounds cold or sarcastic, so keep 해요체 as your everyday setting and save 합쇼체 for the podium, the counter and the broadcast.
• The suggestion -(으)ㅂ시다 has a ceiling. 표준국어대사전 files -(으)ㅂ시다 under the older 하오체 rather than 하십시오체, which is exactly why it does not rise: 갑시다 works among equals or downward, but it can feel presumptuous toward a clear superior. There you soften into a question instead - 가시겠습니까? (gasigetseumnikka?, would you like to go?).
• Learn the frozen ones as whole words. 감사합니다, 안녕하십니까, 실례합니다 and 알겠습니다 are 합쇼체, yet you will use them daily even when the rest of your speech is 해요체. Memorise them as fixed units, not as forms to rebuild.