Verbseoul.
하다 verb
서명하다seomyeonghadato sign (to write one's signature on a document)

To say to sign (to write one's signature on a document) politely in the present tense, use 서명해요 (suh-myuhng-hae-yoh). Below is the full conjugation of 서명하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
서명해
suh-myuhng-hae
서명해요
suh-myuhng-hae-yoh
서명합니다
suh-myuhng-hahm-nee-dah
Past
서명했어
suh-myuhng-hae-ssuh
서명했어요
suh-myuhng-hae-ssuh-yoh
서명했습니다
suh-myuhng-hae-sseum-nee-dah
Future
서명할 거야
suh-myuhng-hahl- -guh-yah
서명할 거예요
suh-myuhng-hahl- -guh-yae-yoh
서명할 겁니다
suh-myuhng-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
서명하세요
suh-myuhng-hah-sae-yoh
Suggestion / Let's Polite (요)
서명해요
suh-myuhng-hae-yoh
Question Polite (요)
서명해요?
suh-myuhng-hae-yoh-?
Connective “and” — (고)
서명하고
suh-myuhng-hah-goh
Conditional “if” — (면)
서명하면
suh-myuhng-hah-myuhn
Noun form — (기)
서명함
suh-myuhng-hahm