From a practical perspective, how do you expect your employer to pay you if they do not know the hours that you worked? It definitely sounds like you work on an hourly basis instead of a salary. Why are you balking at turning in your time cards? As someone who used to prosecute employee embezzlement and fraud, the reluctance to turn in time sheets or time cards were huge red flags to us that something wrong was going on. You need to step out of your shoes and into their shoes to see how this would come off to them and simply provide them with the time cards. That is simply not too much to be asking for.
The information provided in this answer does not create an attorney-client relationship and is not considered to be legal advice.
Yes-they can withhold until you turn in your time card.
How would they know how to pay you or if you worked at all?
The answer given does not imply that an attorney-client relationship has been established and your best course of action is to have legal representation in this matter.
As noted by my colleagues, employers may require that you turn in a time card in order to process payment of wages. To th extent that you might be a salaried and properly classified individual, even then an employer may withhold payment, if their policies are clear about the need for the time card (e.g. in order to invoice clients).
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