Your state, your last day, your rate — and the verdict prints your owed-by date, the penalty in dollars, your vacation verdict, and one total-owed number. Free, and nothing leaves your browser.
In Colorado, Minnesota, Missouri, Utah, Louisiana and Maine, the waiting-time penalty does not begin when the deadline passes. It begins when the employer receives a written demand and still does not pay. Minnesota's statute is the purest form: wages are due "when demanded," and the per-day penalty runs from 24 hours after the demand lands (§181.13). Colorado gives 14 days after the demand before its 200%-or-$1,000 penalty attaches. Workers lose this money every week by asking politely, verbally, for a month.
Threats you cannot execute, numbers you cannot defend, or a penalty presented as guaranteed where the statute requires a willful failure. Overstating the math hands the employer the one defense — good faith — that beats penalties. The letter's power is that every figure in it survives being checked.
If the window closes unpaid, the next artifact is the state wage claim — free in every state that has one, and carrying its own filing deadline (in Texas, 180 days from the due date, and that window does not reopen). The checker tells you which clock your state runs on and when yours closes.