Quarterly Tax Planning: The 90-Day System That Keeps You From Getting Blindsided in April

The pattern I see every March

A trades business owner walks into their CPA's office in March with a shoebox of receipts and last year's bank statements. The CPA does the work, calls them back two weeks later, and says: "You owe $22,000 by April 15."

Owner: "How is that possible?"

CPA: "You made $140,000 in profit last year."

Owner: "Yeah but I already paid quarterly estimates."

CPA: "You paid $4,000 in estimates. That was about right for your prior year. But you grew 40% this year and didn't adjust."

Owner: "...is there anything we can do?"

CPA: "For last year? Not really. We can talk about next year."

This is how 90% of trades businesses do taxes. Reactive. Surprised. Always one step behind.

The owners who pay the least tax (legally) don't do anything dramatic. They just run a quarterly rhythm — checking in with the numbers every 90 days, making small adjustments, and arriving at year-end with no surprises.

Here's the system.

Why quarterly matters more than annual

The big tax-saving moves all have deadlines during the year, not after it. By the time your CPA is finalizing your return in March, almost every meaningful decision is locked in.

Q1 (January – March): Foundation

What you're doing: Closing out last year, setting the table for this year.

Checklist:

• Review last year's tax return — what surprised you? What can you avoid this time?
• File 1099s and W-2s by January 31 (for prior year)
• Reconcile December books — make sure last year is truly closed
• Pay Q4 estimated tax by January 15 (last installment for prior year)
• Confirm entity structure is still right — has revenue grown? S-Corp conversation?
• Set up retirement accounts if you don't have them (SEP-IRA, Solo 401(k))
• Project current-year income based on early signals and last year's actuals
• Pay Q1 estimated tax by April 15 (first installment for current year)
• Schedule a mid-year check-in in June

Time investment: ~3-4 hours, mostly during the document-gathering phase.

Q2 (April – June): Mid-year check

What you're doing: Pulling actual data and adjusting course.

Checklist:

• Pull year-to-date P&L — how does revenue compare to last year? What's your profit margin doing?
• Compare actual results to your January projection — are you running ahead or behind?
• Re-project full-year income based on Q1 results
• Adjust Q2 estimated tax payment if needed (due June 15)
• Review planned equipment purchases — Section 179 timing
• Confirm S-Corp owners are running payroll correctly with reasonable comp on track
• Review AR aging — anything that should be written off?

Time investment: ~2 hours.

Q3 (July – September): The strategic quarter

What you're doing: This is where most of the year's real tax decisions get made. You have enough data to project accurately, and enough time to actually act.

Checklist:

• Pull updated YTD P&L and project full year with confidence
• Get a written tax projection — what's your expected tax liability for the full year?
• Pay Q3 estimated tax by September 15
• Plan year-end equipment and vehicle purchases — Section 179 timing
• Max out retirement contributions — SEP-IRA, Solo 401(k), employer matches
• Review AR for any uncollectible amounts (bad debt deduction)
• Consider deferring December income or accelerating December expenses depending on your projected bracket
• If you're an S-Corp, confirm year-to-date payroll is on track for reasonable comp targets

Time investment: ~4-5 hours including a planning meeting with your CPA. This is the highest-leverage hour of the year.

The Q3 rule: By October 1, you should have a written tax projection that estimates your full-year tax liability within $1,000–$2,000. If you don't, you're flying blind into Q4.

Q4 (October – December): Execute

What you're doing: Pulling the trigger on the moves you planned in Q3.

Checklist:

• Execute equipment and vehicle purchases — must be placed in service by December 31, not just ordered. See: Section 179 & The Trades Truck Deduction.
• Final retirement contributions for the year
• Charitable contributions if part of your plan
• Pre-pay deductible expenses (subscriptions, insurance, professional dues) if it makes tax sense
• Send W-9 requests to subcontractors so 1099s are ready in January
• Run final payroll for the year, including any S-Corp owner adjustments
• Reconcile every account through December
• Document mileage and home office for the year
• Confirm all vehicle and equipment purchases are placed in service (not just ordered)

Time investment: ~6-8 hours, but spread across the quarter.

Q1 of the following year: Wrap up

Back to the top. Issue 1099s and W-2s. Pay Q4 estimate. Compile docs for return prep. Start the cycle again.

What "estimated taxes" actually are

If you're new to self-employment, this part trips a lot of people up.

When you work a W-2 job, your employer withholds taxes from every paycheck and sends them to the IRS throughout the year. By April, you've already paid most of what you owe.

When you're self-employed, you have to do this yourself, four times a year. The IRS expects you to pay taxes as you earn the income — not in one big lump in April. If you wait, they charge underpayment penalties.

The four estimated tax due dates:

• April 15 — Q1 (covers Jan-Mar income)
• June 15 — Q2 (covers Apr-May income)
• September 15 — Q3 (covers Jun-Aug income)
• January 15 of next year — Q4 (covers Sep-Dec income)

Two ways to avoid underpayment penalties ("safe harbor"):

1. Pay at least 100% of last year's total tax (110% if your prior-year AGI was over $150K), OR
2. Pay at least 90% of current year's actual tax through estimates and withholding

Most owners use option 1 because it's simpler. But if your business is growing fast, option 1 leaves you owing a big balance in April. Option 2 requires actually projecting current-year income — which is exactly what the quarterly rhythm above gives you.

The IRS's official guidance lives at IRS.gov — Estimated Taxes.

Why most owners skip this

Three reasons:

1. They don't have the financial visibility. If your books aren't reconciled monthly, you can't project taxes accurately. If you can't project, you can't plan.

2. Their CPA is reactive. Most generic tax preparers don't do quarterly check-ins. They show up in March, do the return, send the bill, and disappear until next March. Quarterly planning isn't part of their service model.

3. It feels like extra work for an uncertain benefit. It's not uncertain. The owners who run this rhythm save thousands of dollars a year compared to the ones who don't — and they sleep better in March.

Putting it all together

The owners who pay the least tax legally aren't doing anything aggressive. They're doing the basics consistently across four 90-day blocks:

1. Q1: Close out last year. Project this year. Pay Q4 + Q1 estimates.
2. Q2: Mid-year check. Compare actual to projection. Adjust.
3. Q3: The strategic quarter. Written projection. Plan year-end moves.
4. Q4: Execute. Place equipment in service. Final retirement contributions. Reconcile.

None of it is complicated. It's just consistent.

Where Northbound fits

If running this math every quarter sounds like one more thing you don't have time for, that's exactly what we do.

Northbound's Growth plan includes quarterly CPA review reports — a written analysis of your P&L, your projected tax liability, and any moves you should make before year-end. It's the rhythm that turns "surprise tax bill in April" into "I knew this was coming, and I already planned for it."

The Compliance Package within Growth also handles your federal and Texas filings on the dates above so you don't have to track them: quarterly estimates, Form 941, Franchise Tax, PIR, 1099-NEC, and W-2/W-3 — all filed and confirmed on time.

Book a free 30-minute discovery call

Related reading

• The Complete Financial Playbook for Texas Trades Businesses
• Section 179 & The Trades Truck Deduction
• Self-Employment Tax Explained for Trades Businesses
• Sole Prop vs. LLC vs. S-Corp for Trades Businesses

Tax figures and deadlines cited are based on 2026 federal tax law including OBBBA-effective changes as of publication. Specific dates can shift due to weekends and holidays; specific limits and rules can change. Confirm current deadlines and figures with the IRS, Texas Comptroller, or a qualified tax professional. Nothing in this article constitutes legal, tax, or financial advice for your specific situation.