Can my previous employer hold my last paycheck for 6 months after I leave the company?

Unlike many states, your state does not have a hard and fast rule about when a final paycheck should be paid. Typically, it's paid when the next payroll would be run for most employees, and a failure to pay it then--or at most, the period after that--would likely be unreasonable and give rise to the ability to sue for the money. You write, however, that you are a commissioned employee. Employers can debit chargebacks, bad debts, returns, etc. from commissions. For current employees, an adjustment due to a late return or bad debt can be corrected on a future check, so there's not too much exposure for the employer. But if you left the company, then there are no future checks to use to make the adjustment therefore, the employer is likely justified in holding the check for the typical period of time it would take to make sure there are no chargebacks, returns, unpaid bills or bad debts, etc., to make sure they don't overpay you. If the 180-day period is close to how long that would usually take, then the delay in payment is probably justified and could be difficult to beat in court. Unless you are desparate for the money, waiting the 180 days may be your best option.