て済む【てすむ】

て済む says that doing something is enough to settle a matter: "~ will take care of it", "you can get away with just ~". The verb in front is in the て-form, and すむ済む, "be settled", changes like any う-verb.

In the positive, て済む mostly comes before なら, or before a noun such as はなし話, こと or もんだい問題.

で済む after a noun

After a noun, で済む says the matter ended at that much and no worse: a small cost, a light injury, a mild punishment. It is said with relief.

ないで済む

After the ない-form with で, 済む says you got out of doing something: "didn't have to". なくてすむ済む and the more formal ずにすむ済む mean the same.

て済む問題ではない

In the negative, the speaker turns down the easy fix: the matter is too serious for that. The negative usually goes on the noun after 済む – て済む問題ではない, て済むことではない, て済む話ではない.

After a noun, the same refusal is ではすまない済まない.