This is sometimes called "wage theft," and it can take many forms.
If your employer isn't paying you for all the time you spend working, isn't paying you what it said it would, isn't paying you for working overtime, or is taking unauthorized deductions from your pay, it may be breaking the law.
Only certain types of jobs are legally "exempt" from receiving overtime. Just because your employer considers you "salaried" or "ineligible" for overtime does not mean you're not owed additional pay when you work more than 40 hours in a week.
Employers are generally prohibited from withholding a portion of your paycheck for things like uniforms, supplies, or theft and breakage, especially if doing so results in you receiving less than the full minimum wage for every hour worked.
Companies that require employees to clock in and clock out sometimes round recorded times to the nearest five, ten, or fifteen-minute mark. Over time, those "lost" minutes can add up to significant unpaid wages.
Employers are generally required to pay you at least the hourly minimum wage for mandatory job-related trainings, seminars, and orientations. If you're required to go through job training for your employer's benefit, that may be considered "working time" that you're owed compensation for.
If you're an hourly employee, your employer can't require or permit you to clock out but keep working. This includes expecting you to complete tasks before going home, encouraging you to work through unpaid breaks, or editing your time sheets without authorization.
In Massachusetts and several other states, employers cannot require you to pay for certain "ordinary business expenses" out of your wages. If you're required to use your personal vehicle for work, for example, your employer must reimburse you for all transportation expenses, including mileage.
Massachusetts requires employers who terminate an employee to pay that employee all earned wages up to the day of termination on the same day as the termination. That includes any accrued, unused PTO, like vacation time.
Whether you're owed a commission often boils down to the commission contract. The contract determines how and what you should be paid. Employers don't always abide by the terms of those contracts when it comes time to actually pay earned commissions.
9-to-5 jobs are becoming a thing of the past. These days, many employers expect employees to be "on call," to "get in early," "stay a little late," or to perform work outside the scheduled workday. That's fine as long as you're getting paid properly.
If you're doing work for your employer and suspect you're not getting paid for doing so, or aren't getting paid everything your employer said you would, you may have a claim for unpaid wages.
Employees in Massachusetts can sue their employer to recover unpaid compensation. Employees who succeed in bringing such lawsuits can recover triple what they're owed. Massachusetts also requires employers to pay prevailing employees their legal fees and costs, as well as interest on any unpaid wages.

A remote technician who installed and repaired manufacturing equipment typically worked between 50 and 60 hours per week. However, his employer paid him a fixed annual salary with no overtime. After reviewing the technician's job duties, we determined he was eligible to receive overtime under Massachusetts law. We calculated he was owed about $65,000 in time-and-a-half pay, which got tripled to $195,000.
A baking company paid its line production workers by the hour. It required them to clock in and clock out at the start and end of their shift, but if workers reported to work early, the company would round their clock-in times to the nearest 15-minute mark, erasing any time they spent working after clocking in early. We ultimately recovered nearly $1 million in unpaid wages for the workers as a result of this "time shaving" practice.
A delivery driver for a national pizza chain wasn't receiving all his tips in his paycheck and wasn't getting paid the minimum wage when he was working "in store" folding boxes and taking orders. We determined he was owed about $6,500 in unpaid tips and wages. That amount then got tripled to about $19,500, which is what we recovered for him. The court awarded us more than $41,000 in legal fees and costs for our work on the case.