が済んだら

when … is finished

→ が
phrase Uncommon #9,644
when … is finished The が marks what is being completed. 済む can also mean to feel satisfied, as in 気が済む.
JA: 仕事が済んだら、電話してください。
EN: When you're finished with work, please call me.

食事が済んだら行きます。

I'll go once I've finished eating.

最後の一つが済んだらね

Once the last one is done.

— ロード・オブ・ザ・リング/王の帰還 (2003)

いいかこいつが済んだら––お前もやってやる

Listen, once I'm done with this guy—I'll deal with you too.

— 28年後... 白骨の神殿 (2026)

ここが済んだら行く

I'll go once I'm done here.

— アバウト・タイム ~愛おしい時間について~ (2013)

書類が済んだら一緒にどうぞ

Once you're done with the paperwork, please come with me.

— Good Luck, Have Fun, Don't Die (2026)

その仕事が済んだら、スタードックを見に行くとのことだった。

They said they’d go see the Star Dock once they’d finished that job.

仕事が済んだら電話するよ。

I’ll call you when I’m done with work.

すべてが済んだらまたバンドをやろう

Once everything is settled, let's get the band back together.

— JUNO/ジュノ (2007)

ここが済んだら、上まで行ってみよう。

Once we're done here, let's go up and take a look.