Part 12: Annual Compliance Calendar

One of the most consistent sources of avoidable penalties in e-commerce is not misunderstanding the law. It is missing deadlines that were perfectly well understood. A quarterly estimated tax payment that slips two weeks past the due date. A sales tax return filed on time in fourteen states and late in one. A W-2 that goes out in February instead of January. A state annual report that was never renewed because no one had it on a calendar.

The compliance obligations of a growing e-commerce business do not announce themselves. They accumulate quietly, and the penalties for missing them arrive without warning. The only reliable defense is a systematic calendar that captures every obligation, every deadline, and every recurring task. This part provides exactly that, organized month by month. All dates assume a calendar tax year. Sellers with a non-calendar fiscal year should adjust accordingly.

January: Year-End Close and First Filings Due

January is the busiest compliance month of the year. Year-end obligations from the prior year land simultaneously with new-year setup tasks.

January 15. Fourth quarter estimated federal and state income tax payments due. This is the final estimated payment for the prior tax year.

January 20 (approx.). Sales tax returns due for December for monthly filers. Confirm the specific deadline for each state, as dates vary.

January 31*. Form W-2 must be furnished to each employee and filed with the Social Security Administration along with Form W-3. Form 1099-NEC must be furnished to each contractor paid $600 or more and filed with the IRS (Paper filers transmit forms with Form 1096). Form 940, the annual FUTA tax return, is due. Form 941 for Q4 payroll taxes is due. State unemployment tax returns for Q4 are typically due at the end of January.

Throughout January: download and save all prior year Amazon settlement reports and platform transaction data. Begin year-end inventory reconciliation. Confirm that ending inventory in your accounting software matches the physical count and the Amazon FBA inventory report.

* - If January 31 falls on a weekend or legal holiday, the due date moves to the next business day. For example, in 2026, January 31 falls on a Saturday, so the deadline moves to February 2, 2026

• January accountant touchpoint: confirm year-end data gathering is underway, prior year books are being closed, and the timeline for filing entity and personal returns is agreed. If your entity return is due March 15, your accountant needs complete financial data by mid-February.

February: Data Gathering and Return Preparation

February 15 (approx.). Form 1099-K forms from Amazon, Shopify, Etsy, PayPal, and other payment processors should arrive by mid-February. Form 1099-K should generally be furnished by January 31, or the next business day if that date falls on a weekend or legal holiday. If not received by mid-February, follow up with the platform or payment processo.

Collect all 1099-Ks, verify amounts against your own records, and document reconciling differences.

February 20 (approx.). Sales tax returns due for January for monthly filers.

Throughout February: reconcile prior year Amazon settlement data. If using A2X, confirm all settlement periods are processed and posted correctly. Review the prior year income statement for anomalies before return preparation begins.

• February accountant touchpoint: deliver complete financial records for return preparation. S-Corp filers should do this in February to allow adequate preparation time before the March 15 entity return deadline.

March: Entity Returns Due

March 15*. Form 1120-S for S-Corps and Form 1065 for partnerships and multi-member LLCs are due. File Form 7004 for an automatic six-month extension to September 15 if needed. Extension extends the time to file, not the time to pay. For pass-through entities, owners may still need to pay their individual tax by April 15, and state/entity-level payments may have separate rules.

Schedule K-1s should be issued to shareholders and partners as soon as the entity return is filed.

March 20 (approx.). Sales tax returns due for February for monthly filers.

March planning touchpoint: review the Q1 estimated tax payment due April 15. If the prior year liability has been calculated, establish the prior-year safe harbor amount and set up the Q1 payment now, not on April 14.

*- March 15, or the next business day if March 15 falls on a weekend or legal holiday.

April: Personal Returns and Q1 Estimated Payments

April 15*. Personal Form 1040 due. File Form 4868 for an automatic six-month extension to October 15 if needed. Any balance due is payable by April 15 regardless of extension. First quarter estimated federal income tax payment due for the current year. First quarter estimated state income tax payments due in states that require quarterly estimates. C-Corp Form 1120 also due April 15 for calendar-year C-Corp.

April 20 (approx.). Sales tax returns due for March for monthly filers and Q1 for quarterly filers. The Q1 quarterly return is the largest filing of the year for quarterly filers and should be prepared with adequate lead time.

April 30. Form 941 for Q1 payroll taxes due.

April nexus review: check economic nexus position for Q1. Have any new state thresholds been crossed? If so, registration should begin immediately. Waiting until year end can sometimes mean a full year of uncollected tax liability in the new state.

*-April 15, or the next business day if April 15 falls on a weekend or legal holiday.

May

May 20 (approx.). Sales tax returns due for April for monthly filers.

May is a relatively quiet compliance month. Use the space to confirm that all April deadlines were met and that there are no outstanding state notices requiring response.

June: Q2 Estimated Payments and Mid-Year Planning

June 15. Second quarter estimated federal and state income tax payments due. Note that Q2 covers only April and May income, as the April 15 payment covered Q1. This uneven spacing is a common source of confusion for first-year estimated tax payers.

June 20 (approx.). Sales tax returns due for May for monthly filers.

• June accountant touchpoint: mid-year tax planning conversation. At this point you have five months of actual results and can project the full year with reasonable accuracy. Review estimated payment calibration, new nexus positions, planned second-half purchases, and whether the current entity structure remains optimal.

July: Q2 Close and Sales Tax Review

July 20 (approx.). Sales tax returns due for June for monthly filers and Q2 for quarterly filers.

July 31. Form 941 for Q2 payroll taxes due. State Q2 unemployment tax returns typically due at the end of July.

Throughout July: review FBA inventory position and nexus exposure at the midpoint of the year. Pull the Inventory Event Detail report from Amazon Seller Central to confirm which states currently have your inventory. Check your sales tax automation platform's nexus dashboard to confirm economic nexus tracking is current.

August: Annual Compliance Review

August 20 (approx.). Sales tax returns due for July for monthly filers.

• August annual compliance review: all states where you are currently registered for sales tax; states where you have nexus but are not registered; income tax nexus positions that have evolved during the year; changes in business model, product mix, or selling channels that create new compliance considerations; status of any outstanding state notices or inquiries. Addressing these in August gives time to resolve issues before year-end.

September: Entity Return Extensions Due and Q3 Planning

September 15. Extended Form 1120-S and Form 1065 returns due if extensions were filed in March. No further extension is available. Third quarter estimated federal and state income tax payments due.

September 20 (approx.). Sales tax returns due for August for monthly filers.

• September Q4 planning touchpoint: last opportunity to implement year-end strategies requiring action before December 31. Review planned asset purchases for Section 179 timing, retirement account contribution strategy, Solo 401(k) establishment if needed, and whether the S-Corp reasonable salary for the year remains defensible given actual profit levels.

October: Personal Return Extensions Due

October 15. Extended personal Form 1040 returns due. Final deadline with no further extension available.

October 20 (approx.). Sales tax returns due for September for monthly filers and Q3 for quarterly filers.

October 31. Form 941 for Q3 payroll taxes due.

October S-Corp election planning: if the S-Corp election would be beneficial and has not yet been made, begin the conversation with your accountant now. Form 2553 must be filed by March 15 of the year the election is to take effect, and payroll needs to be set up before the first salary payment.

November: Year-End Inventory Planning

November 20 (approx.). Sales tax returns due for October for monthly filers.

November inventory planning: year-end inventory decisions affect COGS and reported profit. Review slow-moving or unsaleable inventory for write-down or disposal before December 31. Inventory written down to net realizable value before year end may produce a current-year tax benefit but only if permitted under the taxpayer’s tax inventory method and supported by proper evidence, such as obsolete, damaged, or unsalable goods. Consider whether excess FBA inventory accumulating long-term storage fees warrants a removal order.

December: Year-End Execution

December 15. Practical deadline for large asset purchases intended to be placed in service before December 31 for Section 179 expensing or bonus depreciation in the current year.

December 20 (approx.). Sales tax returns due for November for monthly filers.

December 31. Solo 401(k) plans should be established by this date to accept contributions for the current year (Under SECURE Act changes, some qualified retirement plans may be adopted after year-end and still receive employer contributions for the prior year by the tax filing deadline, including extensions. Employee deferral timing is different and generally must be elected before compensation is paid. IRS guidance confirms employer contributions can generally be made by the employer’s tax filing due date, including extensions).
Charitable contributions intended to be deductible in the current year must be made by December 31. Gifting of business interests to family members using the current year's annual exclusion must be completed by December 31. Any entity elections or structural changes intended to take effect in the new year should be executed before this date.

• December final review: confirm all estimated payments have been made, review whether any prepayments make sense before year end, verify the year's financial picture is consistent with mid-year projections, and identify any surprises requiring attention before filing season opens.

Entity Maintenance: Annual Obligations Beyond Tax Returns

Annual state reports and franchise taxes. Most states require LLCs and corporations to file an annual or biennial report confirming the entity's registered agent, principal address, and ownership information. Filing frequency, deadline, and fee vary by state. California's $800 minimum franchise tax is due April 15 for calendar-year LLCs, but an LLC may also owe the California LLC fee depending on California-source gross receipts.
Delaware's annual franchise tax for corporations is due March 1. Missing these filings can result in the entity losing good standing or being administratively dissolved.

Registered agent renewals. Confirm that your registered agent subscription is current and active in each state where the entity is registered. A lapse in coverage can cause the entity to fall out of good standing.

Foreign entity registrations. If registered as a foreign entity in states other than your state of formation, each state has its own annual report filing and fee. These are separate from home state filings and are easy to overlook if not tracked systematically.

Business licenses and local permits. Some counties and municipalities require local business licenses that must be renewed annually. Review whether any local licensing requirements apply and add renewal dates to the compliance calendar.

When to Engage Your Accountant: The Five Critical Months

Not all months are equal for accountant engagement. The five months where professional input is most valuable are January, March, June, September, and December: the months where year-end data arrives, entity returns are prepared, mid-year projections are made, Q4 planning is implemented, and final year-end decisions are executed.

Sellers who engage their accountant reactively, calling when a problem has already materialized or when a deadline has been missed, consistently pay more in penalties, interest, and rushed professional fees than those who maintain a regular advisory rhythm. The compliance calendar is the tool that makes a proactive relationship possible.

The calendar in this part is a framework. The specific dates for your state sales tax filings, state income tax estimated payments, entity annual report deadlines, and payroll tax deposit schedule all need to be verified and added to your own working calendar based on your specific situation. The framework does not substitute for that verification, but it provides the structure into which the verified specifics slot.

• Antravia Advisory provides year-round compliance management, quarterly review, and annual tax planning for e-commerce sellers. If you would like a compliance calendar built specifically for your business structure and filing obligations, contact our team.

Part 13: Working With Professionals — the final part of this guide — continues next.

About Antravia Advisory

Antravia Advisory is a US-based tax and accounting advisory firm headquartered in Winter Park, Florida, operating nationally and internationally.

We advise international businesses entering the United States and complex US companies operating across multiple states, entities, and revenue structures. Our work spans advanced tax strategy, multi-state sales tax oversight, cross-border structuring, and high-level accounting architecture for e-commerce brands, subscription and SaaS businesses, platform-based models, and multi-entity groups.

We work with founders and leadership teams who require technical precision, structural clarity, and financial frameworks built for scale, capital events, and long-term resilience.

The E-Commerce Seller’s Complete Guide to US Tax, Accounting, and Compliance

Part 1 — The Big Picture

Part 2 — Entity Structure

Part 3 — Sales Tax

Part 4 — Income Tax

Part 5 — Platform-Specific Issues

Part 6 — Bookkeeping and Accounting Architecture

Part 7 — Payroll and Hiring

Part 8 — International Sellers Selling Into the US

Part 9 — Sales Tax Automation

Part 10 — Catching Up

Part 11 — Scaling and Exit Planning

Part 12 — Annual Compliance Calendar

Part 13 — Working With Professionals

Disclaimer:
Content published by Antravia is provided for informational purposes only and reflects research, industry analysis, and our professional perspective. It does not constitute legal, tax, or accounting advice. Regulations vary by jurisdiction, and individual circumstances differ. Readers should seek advice from a qualified professional before making decisions that could affect their business.

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