Tax Landmines: The 7 Dates That Keep You Out of Trouble (CPA Explained)
One missed date can trigger three penalties. Here are the seven IRS deadlines every business owner must hit—plus two simple ways to set quarterly estimates so you never guess again.
Three penalties. One missed date.
Here are the seven deadlines that keep your money—and your sanity. Plus, two simple ways to set quarterly estimates so you never guess again.
Note: Extensions extend filing, not paying.
The quick take
Most IRS pain comes from missed dates, not bad math.
System = calendar + current books + consistent estimates.
Lock in the seven dates, pick one estimate method, and pay by the original due dates.
The fast map (all dates at a glance)
Jan 31 — W‑2s & 1099‑NEC to workers and filed (SSA/IRS).
Mar 15 — S‑Corp (1120‑S) & Partnership (1065) returns due (or extend).
Apr 15 — Individual 1040 due + Q1 estimates. Calendar‑year C‑Corps (1120) also file now.
Jun 15 — Q2 estimates due.
Sep 15 — Q3 estimates due + S‑Corp/Partnership final (if extended).
Oct 15 — Individual final (if extended).
Dec 31 — Last day for most year‑end strategies (comp, assets, reimbursements).
Jan 15 (next year) — Q4 estimates due (note: Jan 15, not Jan 31).
Prefer a one‑page checklist? Open our Tax Playbook & Estimator for all dates at a glance and a built‑in estimator.
What “extension” really means
Extensions give you more time to file, not more time to pay.
If you don’t pay enough by the original due date, you’ll rack up failure‑to‑pay and interest.
Bottom line: Pay by the original date. File later if you must.
Quarterly estimates — two ways to set them
Pick one method and stay consistent:
Method 1: Prior‑Year Safe Harbor (easy mode)
- Pay 100% of last year’s total tax (110% if prior‑year AGI > $150k MFJ / $75k MFS).
- Divide into four equal payments due Apr 15, Jun 15, Sep 15, Jan 15.
Use when: income is steady and you want a simple penalty shield.
Method 2: Rolling P&L (precision mode)
- Use year‑to‑date profit each quarter to compute what you actually owe.
- Requires books closed by the 15th monthly.
Use when: income swings (seasonal/project‑based) and your books are disciplined.
How to pay: IRS Direct Pay or EFTPS (save confirmations). States have their own portals/dates—set those too.
Tool: Compare methods and auto‑compute targets in our Tax Playbook & Estimator.
Date #1–#2: Jan 31 & Mar 15
Jan 31 — W‑2s & 1099‑NEC
Send W‑2s to employees and 1099‑NEC to contractors and file with SSA/IRS.
Prevent notices: Clean your vendor list by Dec 15 and collect W‑9s before you pay vendors.
Mar 15 — S‑Corp (1120‑S) & Partnership (1065)
File the return or file an extension.
If you extend, pay what you expect to owe now to avoid failure‑to‑pay and interest.
Date #3: Apr 15 (+ C‑Corp note)
Apr 15 — Individual returns due + Q1 estimates.
Calendar‑year C‑Corps also file Form 1120 now.
If you extend, send payment with the extension to limit interest.
Dates #4–#6: Jun 15, Sep 15, Oct 15
- Jun 15 — Q2 estimates
- Sep 15 — Q3 estimates + S‑Corp/Partnership final if extended
- Oct 15 — Individual returns final if extended
Tip: Put calendar reminders at 30 / 14 / 7 days ahead of each date.
Date #7: Dec 31 — Strategy deadline
This is where strategy either lives or dies:
- Owner payroll (S‑Corp reasonable comp) set before year‑end
- Fixed‑asset buys & bonus depreciation timing
- Retirement plan setup (adoption vs. funding deadlines vary)
- Accountable reimbursements (home office, mileage, phone) recorded this year
After Dec 31, many levers are gone until next year.
Your simple system
Make this boring and automatic:
- Calendar these seven dates (plus Jan 15) with reminders 30/14/7 days out.
- Close books monthly by the 15th.
- Pick Safe Harbor or Rolling P&L—don’t switch mid‑year.
- Pay via Direct Pay/EFTPS and save confirmations.
- Bookmark: Tax Playbook & Estimator for deadlines + calculator.
Quick wins you can do today
- Lock the dates on your calendar (federal + your state).
- Pre‑flight Jan 31: vendor W‑9s, worker statuses, addresses, and e‑file setup.
- Choose your method: Safe Harbor vs. Rolling P&L; schedule the next payment.
- Reserve cash: earmark funds for Q1/Q2 estimates now.
How HavenStone helps
Our process for busy owners:
- Calendar & cadence: We load the seven dates, reminders, and a monthly close rhythm.
- Entity & workflow audit: Extensions, estimate method, vendor/worker files.
- Implementation: Estimate calculator (Safe Harbor vs. Rolling P&L), payment workflows (Direct Pay/EFTPS), and extension‑with‑payment playbooks.
- Monitoring: Quarter‑by‑quarter variance checks so you stay penalty‑proof.
You’ll know what to do, why it matters, and the dollar impact.
Common questions
How do I decide between Safe Harbor and Rolling P&L?
If your income swings, Rolling P&L can reduce overpaying—but only if books are current. If you want simple penalty protection, Safe Harbor works.
Is Jan 15 the last estimate, not Jan 31?
Correct—Q4 is due Jan 15 (next year) for most individuals (moves to the next business day if it lands on a weekend/holiday).
We’re an S‑Corp on extension—what’s the real risk?
Extensions are fine, but pay by Mar 15 (calendar‑year) to avoid failure‑to‑pay and interest. File by the extended September deadline.
Where can I see all dates and calculate estimates?
Use our Tax Playbook & Estimator for a one‑page deadline map and a quick calculator.
What to do next
Simple start: Put the seven dates (plus Jan 15) on your calendar and pick your estimate method today.
Grab the tools: Open the Tax Playbook & Estimator to view deadlines and calculate your quarterly targets (Safe Harbor vs. Rolling P&L).
Full service: with HavenStone. We’ll map your deadlines, set your estimate method, and build a no‑drama payment system you can run in 15 minutes a quarter.
Compliance note: This article is educational, not tax advice. Federal/state dates and rules can vary by entity, year, and facts. Work with your CPA.