back pay

「滞った支払、未払給料（賃金）」。

back paymentとも言います。

The New York Timesの記事、'Japan Training Program Is Said to Exploit Workers' by HIROKO TABUCHIから。

'HIROSHIMA, Japan — Six young Chinese women arrived in this historic city three summers ago, among the tens of thousands of apprentices brought to Japan each year on the promise of job training, good pay and a chance at a better life back home.

Instead, the women say, they were subjected to 16-hour workdays assembling cellphones at below the minimum wage, with little training of any sort, all under the auspices of a government-approved “foreign trainee” program that critics call industrial Japan’s dirty secret.

“My head hurt, my throat stung,” said Zhang Yuwei, 23, who operated a machine that printed cellphone keypads, battling fumes that she said made the air so noxious that managers would tell Japanese employees to avoid her work area.

Ms. Zhang says she was let go last month after her employer found that she and five compatriots had complained to a social worker about their work conditions. A Japanese lawyer is now helping the group sue their former employer, seeking back pay and damages totaling $207,000'.