Schneiderman’s letter, sent on Friday, alleges that on-call systems leave “too little time to make arrangements for family needs, let alone to find an alternative source of income to compensate for the lost pay” on days the workers are not called in to work.

Some employers require on-call workers to check by phone, email or text message shortly before their designated shift whether their services are needed that day, according to the letter seen by Reuters.

Practices such as on-call scheduling may violate a New York law, according to the letter. Employers in New York are subject to a rule that says employees who report for a scheduled shift on any day have to be paid for at least four hours at the basic minimum hourly wage.

Letters were also sent to Abercrombie & Fitch, J. Crew, L Brands Inc, Burlington Coat Factory, TJX Cos, Urban Outfitters Inc, Crocs Inc, Ann Inc, Sears Holdings, Williams-Sonoma Inc and JC Penney.

Schneiderman asked the retailers to provide details on the processes they follow to schedule on-call shifts such as whether they use computerized systems and penalize employees who do not follow on-call procedures.

He also asked the companies for any analysis that they may have conducted on the cost savings associated with on-call shifts and the impact on workers’ well-being.

“Gap Inc is committed to establishing sustainable scheduling practices,” a spokeswoman said.

The retailer said it was engaged in a research project with the UC Hastings College of Worklife Law to examine workplace scheduling and productivity, and expects to receive some data in the fall of 2015.

“In the meantime, each of our brands also has been working to evaluate and refine their practices to make improvements,” the spokeswoman said.

The companies have until May 4 to send in their responses.

Representatives of the other 12 retailers did not immediately respond to requests for comment.