When does economic nexus begin — the day I cross the threshold or the next period?

In most states, your collection obligation begins on the first day of the following calendar month after you cross the economic nexus threshold, not on the exact day you crossed it. A few states start the clock even faster; a few allow a full quarter buffer.

The practical takeaway: you don’t need to pause mid-month and immediately reconfigure your store. But you need to register and be ready to collect before that first-of-month date arrives.

The three most common start-date rules

First of the following calendar month (most common). You cross $100K in Michigan on October 14. Your collection obligation begins November 1. You have about two weeks to get a Michigan permit and configure collection.

First of the following calendar quarter. A smaller number of states (often SST member states) allow a full quarter buffer. Crossing the threshold in Q3 means your obligation starts at the beginning of Q4. This gives more time to register, but check whether your specific state uses this rule before assuming it.

Next transaction (a few states). Some states take a stricter position: nexus begins immediately on the next sale after the threshold is crossed. In these states, the sale that pushes you over doesn’t trigger collection, but the very next order does.

The safest default for any state you haven’t explicitly verified: assume the obligation begins the first of the following month and register accordingly.

What to do the moment you identify a crossing

Registration takes 1–6 weeks in most states. California can take longer. Don’t wait until the day before your obligation starts.

When you identify that you’ve crossed or are about to cross in a state:

1. Start the registration process immediately
2. Check whether your state uses a month-start, quarter-start, or next-transaction rule
3. Set your collection start date in your platform to match the rule
4. Don’t start collecting before your permit is active, collecting without a permit creates its own compliance issues

If the obligation start date arrives before your permit comes through (which happens when California or other slow-processing states take longer than a month), collect from your permit effective date and retain documentation of the delay.

The threshold crossing date itself

The sale that causes you to cross the threshold is typically not your first taxable collection. Most states set the obligation as starting on future transactions after the crossing, so that specific order is still treated as pre-nexus and no collection is required on it.

This is an important nuance: you don’t retroactively tax the order that triggered nexus. You start from the next one.

Does crossing in December mean starting January 1?

Yes, under the standard first-of-following-month rule, a crossing in December triggers collection starting January 1. This is one of the more manageable scenarios because you have the holiday-to-new-year window to register and configure your store.

A crossing in November is tighter: obligation starts December 1, and registration may take 2–4 weeks, meaning you need to move quickly.

Related: Is there a grace period between crossing a threshold and when I must register? | What do I do the moment I cross an economic nexus threshold?