March brings the end of Q1, which means monthly filing deadlines continue, quarterly filing deadlines are approaching, and annual filings are due in just a few weeks.

Whether you're a founder juggling a dozen priorities, a controller keeping the books straight, or an accountant managing clients across multiple states, here's your quick guide to staying on track this month.

Week of March 2–6

Reconcile February sales data

• Pull February transaction reports from Shopify, Stripe, Chargebee, Amazon, or another platform where your revenue lives.

• Cross-check what you collected against what you actually owe by state.

• Flag discrepancies now: don't let them snowball into headaches as you close off the quarter. 

Review nexus status

• Did February push you over an economic nexus threshold in any new states?

• Reminder: Illinois dropped its 200-transaction threshold on January 1, so now it's purely revenue-based at $100K. If you're a high-volume, low-AOV seller, your exposure just changed. 

• If you crossed a threshold, register before you file.

Week of March 9–13

Prepare for monthly filing deadlines

• Monthly filers: most returns are due March 20th.

• ⚠️ Nevada moved its deadline to the 20th of the month. Update your calendar!

• Gather state portal credentials. 

• Confirm that collected tax is sitting in your account and ready to remit.

Handle outstanding state notices

• Any nexus questionnaires or compliance letters from February still sitting in your inbox? Respond to them right away to avoid delays. 

• States don't wait: delays turn notices into penalties.

Week of March 16–20

File monthly returns

• Filing in 10+ states manually? Set aside 2-3 full days.

• Don't forget local jurisdictions, especially in states like Alabama where city-level rates changed in February.

• Save every confirmation number.

Check exemption certificates

• B2B sellers: are your exempt customer certificates still current? Expired certificates mean you should have been collecting tax…and now you're on the hook.

• If you've added new wholesale or resale customers recently, make sure documentation is in order before Q1 closes.

Week of March 23–31

Get ahead of Q1 quarterly filings (due in April)

• Quarterly filers: Q1 data covers January, February, and March. Start organizing now.

• Pull reports, check for any states where you might have crossed nexus mid-quarter.

Audit your process

• How many hours did compliance consume this month?

• If the honest answer is "too many," that's useful data. Businesses that file in 15+ states spend 2-3 days per month on manual sales tax. 

There's a Better Way

Prepping for monthly sales tax compliance can be exhausting, especially if you’re preparing for quarterly and annual filing at the same time. Sales tax compliance across multiple states is incredibly complex, and it only gets trickier and more high-stakes as you grow into new markets, add sales channels, or cross nexus thresholds you didn't see coming.

Kintsugi automates the parts that shouldn't require a human: nexus monitoring, rate calculations, filing prep, and remittance across all 50 states and 60+ countries. When states change rules, Kintsugi updates automatically so you don't have to.