Verbseoul.
하다 verb
보장하다bojanghadato guarantee, to assure

To say to guarantee, to assure politely in the present tense, use 보장해요 (boh-chahng-hae-yoh). Below is the full conjugation of 보장하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
보장해
boh-chahng-hae
보장해요
boh-chahng-hae-yoh
보장합니다
boh-chahng-hahm-nee-dah
Past
보장했어
boh-chahng-hae-ssuh
보장했어요
boh-chahng-hae-ssuh-yoh
보장했습니다
boh-chahng-hae-sseum-nee-dah
Future
보장할 거야
boh-chahng-hahl- -guh-yah
보장할 거예요
boh-chahng-hahl- -guh-yae-yoh
보장할 겁니다
boh-chahng-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
보장하세요
boh-chahng-hah-sae-yoh
Suggestion / Let's Polite (요)
보장해요
boh-chahng-hae-yoh
Question Polite (요)
보장해요?
boh-chahng-hae-yoh-?
Connective “and” — (고)
보장하고
boh-chahng-hah-goh
Conditional “if” — (면)
보장하면
boh-chahng-hah-myuhn
Noun form — (기)
보장함
boh-chahng-hahm