GRAMMAR DETAIL

〜ないで済む

to avoid having to · not to need to

Indicates that preparation or circumstances make an inconvenient action unnecessary.

Examples

事前に予約したので長い列に並ばないで済んだ。

Because I reserved in advance, I did not have to stand in a long line.

早く出発したので渋滞に巻き込まれないで済んだ。

Because we left early, we managed to avoid getting caught in traffic.

Structure: Add で済む（ですむ） to a verb's ない form to express avoiding a burden or resolving matters without an action.
Basic usage: 事前に予約したので長い列に並ばないで済んだ。 describes avoiding the burden of queuing thanks to a reservation.

Permission and a resolved outcome
- 並ばなくてもいい expresses permission or lack of necessity to queue. 並ばないで済んだ focuses on circumstances actually allowing things to be resolved without that burden.
Avoiding an action and negating resolution
- 払わないで済む means being able to avoid payment, while 払わないでは済まない means that matters cannot be resolved without paying. Negating 済む makes the action necessary.