Can my employer deduct cash shortages with written consent?

I am a lawyer in CT and practice in this area of the law.  Employment agreements are governed by contract law.  if you agree to wage deductions with respect to cash shortages when you begin your employment, your are giving your employer the right to deduct the wages from your paycheck.  i suggest that you hire a lawyer in your state to determine whether there is a statute that outlaws this contract as the contract will not be enforceable if the state has determined by statute that employer and employees may not agree to a contract like this.  most lawyers will meet with you initially for free.

This is a good news/bad news scenario.  The good news is that your employer cannot take the money out of your check unless you agree or if the terms of your employment say that they can.  For example, if there was a stated company policy, or an employment/union contract provided for this, or you were being singled out and discriminated against (based on race, age, religion, sex, disability or any other protected class). 

However, the bad news is, that your boss could fire you for the mistake or give you the choice of repaying the money or being fired (although legally you'd have the right to not pay).  If fact, as an "at will" employee, your employer could fire you for no reason at all.

Note:  If such a policy is instituted, it cannot be applied retroactively.  It can only apply to any shortage situations going forward.