CASH FLOW

FOUR FIXED DATES. MONEY WITH NO SCHEDULE.

QUICK ANSWER

Estimated tax is due on four fixed dates and collections are not. A $5M subcontractor netting 8 percent has roughly $400,000 of taxable income, and at a 30 percent blended rate that is about $120,000 a year, or $30,000 a quarter, leaving the business on dates it does not choose. Two of those dates are the problem: September 15 comes at peak season when working capital is already committed to open jobs, and January 15 comes in the winter trough when collections are slowest. The federal rules give you two ways not to be surprised, a safe harbour and the annualized installment method, and the cash side gives you a third that counts for more, which is funding the liability per invoice and never per quarter.

None of this is a tax position and none of it changes what you owe. It decides whether the money is there on the fifteenth.

BY JOSH LUEBKERPublished 2026-08-21Updated 2026-08-21
THE DEFINITION

WHAT IT MEANS.

Quarterly estimated tax is the federal requirement to pay income tax as it is earned across four installments, due April 15, June 15, September 15 and January 15 of the following year, and for a subcontractor it behaves as four large outflows on dates that have nothing to do with when a general contractor pays.

SPM is not a CPA firm, does not file returns and does not do payroll. This page covers the cash flow consequence of the payment schedule, which is a forecasting problem. Every threshold below is a published federal rule and every judgement about your filing position belongs to your CPA.

WHY THIS HITS CONSTRUCTION HARDER

FOUR DATES AGAINST A SEASON.

01

The dates were not written for seasonal work

April 15, June 15, September 15 and January 15. Three of the four fall inside the building season and the fourth falls in the trough. A contractor whose revenue is concentrated between April and October is paying tax on money earned in a season out of an account that is either funding open jobs or waiting out winter.

02

September 15 competes with your own working capital

Mid-September is when a subcontractor has the most cash committed to open work: material bought, labor run, and pay applications submitted against retainage. That is the moment the third installment is due, and it is due in full whether or not the August pay applications cleared.

03

January 15 falls in the trough

The fourth installment is due when collections on a season's closing invoices are slowest, retainage on completed work has not released, and northern trades are running fixed overhead against very little revenue. It is the same month a lot of contractors discover their line of credit is doing work it was never sized for.

04

Profit and cash are on different clocks, and tax follows profit

The liability is calculated on earned income, and the bank account only knows what cleared. A job finished in August is taxable in that year even if the retainage on it releases the following spring. That distance is what makes a profitable year and a tight January the same year.

THE ARITHMETIC

WHAT IT LOOKS LIKE IN DOLLARS.

The threshold that starts the obligation

Estimated payments are generally required when you expect to owe $1,000 or more for the year beyond what has been withheld. For an owner taking distributions from a pass-through entity, that threshold is cleared early and easily.

The safe harbour, in two forms

The penalty is generally avoided by paying 90 percent of the current year's tax or 100 percent of the prior year's, whichever is smaller. Above $150,000 of prior year adjusted gross income the prior year figure rises to 110 percent. Paying the prior year number is the one that can be budgeted in January, because it is a known figure.

What a $5M sub is funding

At 8 percent net on $5M, roughly $400,000 of taxable income. At a 30 percent blended rate that is about $120,000 for the year and roughly $30,000 an installment. Both the rate and the split depend on entity and state, which is a CPA's call; the point is the size of the number set against a monthly pay application.

The reserve rate that funds it per invoice

$120,000 a year against $5M of revenue is 2.4 percent of every dollar collected. Moving 2.4 percent of each deposit into a separate account funds all four installments out of the season that produced them, without a decision in September.

The uneven income provision

The annualized installment method on Form 2210 lets a taxpayer whose income comes in unevenly compute each installment on the income earned by that point in the year and never on a flat quarter. It exists for seasonal businesses, and construction is one.

HOW TO STOP BEING SURPRISED

FUND IT PER INVOICE. NEVER PER QUARTER.

Put the four dates in the cash forecast as line items

Most 13 week forecasts carry payroll, material and debt service and stop there. The installments belong on the same forecast at the same weight, because they are the same kind of event: a known amount on a known date that does not negotiate.

Move a fixed percentage of every collection, on the day it clears

Take the prior year liability, divide by prior year revenue, and move that percentage out of every deposit the day it clears. The account funds itself in proportion to the work that created the liability, and the September decision disappears because it was made in April.

Ask your CPA about annualizing before the year is over

The annualized installment method has to be applied to a year, and the figures it needs are quarter by quarter income and cost. That is a job costing question before it is a tax question, and books closed monthly can answer it while there is still a quarter left to change.

Size the line of credit against January, not against the average

A credit line sized on average working capital will be short in the month that carries the fourth installment, the winter overhead and the slowest collections at once. The peak draw is what the facility has to cover, and January is usually where the peak is.

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COMMON QUESTIONS

FREQUENTLY ASKED.

April 15, June 15 and September 15 of the current year, and January 15 of the following year. The intervals are not equal quarters, which catches people out: the second installment is due two months after the first, and the fourth is four months after the third.
Generally 90 percent of the current year's tax or 100 percent of the prior year's, whichever is smaller, and 110 percent of the prior year where prior year adjusted gross income was above $150,000. There is also a de minimis rule: no penalty where the amount owed beyond withholding is under $1,000. Your CPA settles which figure applies to you.
The annualized installment method on Form 2210 computes each installment on income earned by that point in the year, which is the provision written for businesses whose money comes in unevenly. Using it requires quarter by quarter income and cost figures, so it depends on books that close monthly and never at year end.
A defensible starting point is prior year tax liability divided by prior year revenue, moved out of every deposit as it clears. On a $5M business carrying a $120,000 liability that is 2.4 percent. It funds the installments out of the season that earned them and takes the decision out of September.
No. SPM is not a CPA firm, does not file returns and does not run payroll. What SPM does is produce job costed books and a cash forecast the four installments sit inside, so the amounts are known in advance and your CPA is working from figures that are already closed.
WHAT THIS TIES INTO
Josh Luebker, The Construction CFO
Josh Luebker
FRACTIONAL CFO · THE CONSTRUCTION CFO

Former commercial project manager and master electrician: 150+ projects worth $2.1B combined, from $50,000 to $300M. Now fractional CFO to commercial subcontractors.

IS THE FIFTEENTH ALREADY FUNDED?

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