ずにはすまない
Won't get away without, Won't get off without, Have to, Have no choice but to, Can’t not
Structure
Verb[ない] + では + すまない
Exception:
する→せずにはすまない
Explanation
ずにはすまない expresses that, due to social norms or one's circumstances, one is obligated to do (A). It carries the nuance that 'one must do (A)' or 'it would be unacceptable not to do (A)'. This formal phrase is constructed from the classical negative auxiliary verb ず, the particles に and は, and the verb 済む in its negative form. A very literal interpretation would be 'it will not be finished/resolved without doing (A)', which reflects the sense of unavoidable responsibility.
Because this grammar pattern begins with the negative auxiliary ず, it is always attached to the stem of a verb.
- 規則を破った以上、罰を受けずにはすまないだろう。Since I broke the rules, I probably won't get away without being punished.
- お世話になった先輩が転勤するので、送別会を開かずにはすまない。A senior colleague who has helped me a lot is transferring, so we have no choice but to throw a farewell party.
- 人から借りたお金は、きちんと返さずにはすまない。Money you borrow from someone, you have no choice but to pay it back properly.
When this grammar is used with the verb する, it takes the special form せず, not しず.
- こんなにひどいことをしたのだから、謝罪せずにはすまない。After doing something so terrible, I have no choice but to formally apologize.
The ない-form of a verb followed by ではすまない can be used as an alternative. This variation carries the exact same meaning as ずにはすまない.
- 車で事故を起こしてしまったら、警察に連絡しないではすまない。If you cause a car accident, you have no choice but to contact the police.
- 人前で約束したのだから、実行しないではすまない。Since I made a promise in public, I can't get away with not following through.
Caution
This grammar point sounds most natural when the obligation to do (A) stems from social conventions, rules, or logic. It is generally not used for actions that are necessary based only on one's private emotions or desires.
Examples
大事な花瓶を割ってしまったのだから、弁償しないではすまない。
I've broken a valuable vase, so I can't get away without paying for it.
会社の信用に関わる大きなミスだ。報告せずにはすまない。
This is a huge mistake that affects the company's credibility. I have no choice but to report it.
人をはねてしまったのだから、警察を呼ばないではすまない。
Since I hit someone with my car, I can't get away with not calling the police.
契約を破ったのだから、違約金を払わずにはすまないだろう。
Since they broke the contract, they'll surely have to pay the penalty fee.
部下の失敗は上司の責任だ。責任を取らずにはすまない。
A subordinate's failure is their boss's responsibility. I have no choice but to take responsibility.
こんなに迷惑をかけたのだから、謝罪しないではすまない。
After causing so much trouble, I won't get away without offering a formal apology.