Ok, I think everyone is getting caught up on calling this a cash register shortage. It's clearly not. Let's more appropriate refer to it as loss of employer property, whether or not due to employee negligence. With that in mind, I still haven't seen a citation to the FLSA, the CFR, a Department of Labor fact sheet or opinion, or anything else that says such a deduction is not possible.

Missouri law places no restrictions on deductions, instead deferring to federal law. And despite an immense amount of searching, I've come up empty handed. All I can find is that the FLSA prevents deductions that bring a non-exempt worker's wages below the prevailing minimum wage.

In fact, the only authoritative reference I could find was a DoL Fact Sheet #16, which mentions:

In other words, no deduction may be made from an employee's wages which would reduce the employee's earnings below the required minimum wageor overtime compensation.

Some examples of items which would be considered to be for the benefit or convenience of the employer are tools used in the employee's work, damages to the employer's property by the employee or any other individuals, financial losses due to clients/customers not paying bills, and theft of the employer's property by the employee or other individuals. Employees may not be required to pay for any of the cost of such items if, by so doing, their wages would be reduced below the required minimum wage or overtime compensation. This is true even if an economic loss suffered by the employer is due to the employee's negligence.

So, provided the employer compensates the employees for the extra hours required to be worked (including any overtime adjustments), and then docks that pay, so long as the employee's take-home is at or above the minimum wage, what is preventing the employer from doing this?