Washington excise tax due dates: monthly, quarterly, and annual

Washington's combined excise return (your B&O tax plus any sales tax you collected) is the filing every registered business owes, on a schedule the Department of Revenue picked for you. Here is when yours is due, and what the late math looks like.

Your due date depends on your assigned frequency

When you registered, DOR assigned you a filing frequency based on your expected revenue: monthly, quarterly, or annual. You don't choose it, and DOR can change it as your revenue changes. The assignment letter is easy to miss, and My DOR shows it under your account's filing schedule.

Source and current dates: DOR — filing frequencies and due dates. Dates falling on weekends or holidays roll to the next business day.

Zero revenue does not mean zero filing

The mistake that catches the most new and seasonal businesses: a slow month is not a skipped month. If you're registered and open, DOR expects a return on your schedule even when the answer is "no business activity." The no-activity return takes about two minutes in My DOR. Not filing it looks identical to hiding revenue until you clear it up.

What late actually costs

Washington's late-filing penalty is not a flat fee — it's a percentage of the tax due that steps up the longer you wait, currently running through 9%, 19%, and 29% tiers as months pass, with interest on top. Confirm the current tiers on DOR's late filing page. Two things make it worse than it sounds:

First, the percentages apply per return, so one forgotten quarter that also delays the next one compounds. Second, unpaid excise tax is one of the debts that can follow the owner personally in a closure — walking away from the LLC does not walk away from trust-fund taxes like collected sales tax.

The pattern behind missed returns

Almost nobody misses the excise return because they can't afford the tax. They miss it because nothing reminded them: DOR sends limited notices, the due date lives in an online portal you log into four times a year, and the 25th-of-the-month cadence for monthly filers never lines up with anything else on your calendar. The fix is boring: put every due date on a calendar the day DOR assigns your frequency, or use a service that does it for you.