In Missouri, your final paycheck is due immediately, at the time of dismissal if you are fired, and no law if you quit.
Final paycheck deadline in Missouri
What your final pay must include
Your final paycheck must include all the wages you earned through your last day. Whether it also has to include unused vacation depends on your state and your employer's policy, some states treat accrued vacation as wages that must be paid out. See Missouri PTO payout rules. If an employer misses the deadline, many states add penalties. This is general information, not legal advice.