Countertop Fabrication Estimated Taxes: Deposits, Slab Purchases, and the CNC Year That Erases the Quarter

Countertop shops meet the estimated tax system with three distortions between cash and profit, and the installments have to be computed on profit. The rules (the contractor estimated-tax guide covers the mechanics): quarterly installments on April 15, June 15, September 15, and January 15; a quarter-by-quarter underpayment penalty; avoided by the prior-year safe harbor (100% of last year's tax, 110% above US$150,000 of prior-year adjusted gross income) in equal installments, 90% of the current year's tax in equal installments, or the annualized method. The three distortions. Deposits: a countertop job takes a 50% deposit at contract (before templating, before the slab is cut), a progress payment at template or fabrication, and the balance at install — so a busy signing month puts cash in the account that the slab purchases and fabrication labor will consume over the following weeks; under the cash method (most shops elect it for tax), deposits are income when received, so the tax computation does follow cash — but the estimate should run on the year's projected profit, and the shop's job-cost system (the cabinet estimated-tax guide's deposits-are-liabilities discipline) books deposits as customer liabilities for management purposes so the owner sees profit, not the March bank balance. Slab purchases: slabs are inventory (the countertop deductions guide) — under the small-business method, deducted as consumed on jobs, not when bought — so a shop that buys a container of quartz in October has spent cash that is not yet a deduction (the slabs on the rack at year-end are not deductible until cut), and a shop that expenses slabs at purchase has a cost of goods sold that runs ahead of the jobs and an estimate that understates the year's tax; the year-end rack count is what makes the fourth installment right. Equipment: a CNC saw-jet or a bridge saw placed in service and expensed under section 179 or bonus depreciation (the deductions guide) can cut the year's taxable profit by six figures — a shop that paid the prior-year safe harbor's installments through September and bought a US$285,000 CNC in October has overpaid the year by the tax on the write-off; the fall recompute (or the current-year method, where the purchase is planned) captures it, and the purchase's timing — placed in service in December of this year or January of next — is a planning lever decided with the estimated-tax picture in view. The seasonal shape: the kitchen and bath remodel cycle puts signings in late winter and spring (summer projects) and again in late summer (fall projects before the holidays), fabrication and installs through spring and fall, and a trough from mid-December through January — milder than a chimney sweep's season and pronounced enough that equal installments overpay in the trough; the annualized method follows the cycle. The two strategies. Prior-year safe harbor with a reserve: four equal installments of last year's tax, funded from a reserve percentage of every deposit and draw (for most shops 25% to 35% of net profit, applied as a share of receipts through the shop's margin — a shop with a 20% net margin and a 32% effective rate reserves about 6.5% of every receipt) moved to a tax account by rule — penalty-proof, with the spring deposits funding the reserve early and the fall recompute adjusting the fourth installment in an equipment year. The annualized method: installments computed on year-to-date cash income less expenses under the cash method (deposits received are income; slabs consumed are cost; slabs on the rack are not), annualized — with Form 2210 Schedule AI at filing; the method suits a shop with a current job-cost system and a pronounced remodel cycle, and it handles the equipment year in the fourth computation. The S corporation shop (the countertop entity guide): the owner's salary withholding covers the tax on salary and projected distributions — deemed paid evenly across the year regardless of when withheld — with a fall adjustment for the CNC and a December payroll curing any shortfall; the shop's payroll for fabricators and installers makes the mechanism routine. What the estimate includes: federal income tax on projected profit; self-employment tax for Schedule C owners (the omitted third — with the wage-base drop above it); the state's estimates; the crew payroll and workers' compensation as costs in the projection; the silica compliance costs (the deductions guide — recurring and equipment); the equipment write-offs (the fall recompute's main item); and — for a shop with a large slab inventory — the year-end count's effect on cost of goods sold. The quarterly check: signings and deposits against projection (the remodel cycle's timing); slabs bought versus slabs consumed (the rack's growth or drawdown); fabrication and install labor against the jobs; equipment purchases planned or made; profit through the quarter (job-cost profit, not the bank balance) annualized against installments or withholding; and the adjustment. The failure modes: paying on the March deposit balance (overpaying, then cash-poor when the slab container and the fabrication payroll land in April and May); expensing slabs at purchase (an understated estimate and a year-end surprise when the count corrects it); paying the safe harbor blindly through a CNC year (a six-figure write-off's tax overpaid and refunded a year later — a year of interest on the equipment loan the refund could have paid); omitting self-employment tax; and skipping the January installment because the trough left no cash (a fourth-quarter penalty on the fall's real profit). The calendar: January — last year closed (the rack count finalized, cost of goods sold set), the safe harbor computed, the reserve percentage set (or the S corporation owner's W-4), the year's equipment plan noted; each deposit and draw — reserve by rule; quarterly — the check; April 15, June 15, September 15, January 15 — installments (or the withholding running); October–November — the fall recompute for equipment placed in service, the slab inventory's trajectory, and the year's actual profit; December — the rack count; filing — Form 2210 Schedule AI if annualized.

Key takeaways

• Three distortions between cash and profit: deposits (cash before the slab is cut), slab purchases (cash before the deduction — slabs on the rack aren't deductible until consumed), and equipment (a CNC write-off that erases a quarter's tax) — estimate on job-cost profit, not the bank balance.
• The remodel cycle puts deposits in late winter/spring and late summer, with a December–January trough — the annualized method follows it; equal installments overpay in the trough.
• Prior-year safe harbor with a reserve (a margin-calibrated share of every receipt) or the annualized method with Form 2210 Schedule AI — both need the fall recompute in an equipment year.
• S corporation shops use salary withholding through the crew's payroll, deemed paid evenly, with a fall adjustment for the CNC.
• Include self-employment tax, the state, the crew payroll, silica compliance, and the year-end rack count's effect on cost of goods sold.
• Never pay the safe harbor blindly through a CNC year — the write-off's tax overpaid is a year of interest on the equipment loan.

The countertop shop's estimated-tax calendar

January: last year closed; rack count finalized; safe harbor; reserve percentage (effective rate × margin) or W-4; equipment plan noted. Each receipt: reserve by rule. Quarterly: signings, deposits, slabs bought vs consumed, labor vs jobs, job-cost profit annualized; adjust. Four dates. October–November: fall recompute — equipment placed in service, slab trajectory, actual profit; adjust the fourth installment or the December withholding. December: rack count. Filing: Schedule AI if annualized. The slab line and the equipment line are the ones no general routine has.

Worked example

A fabrication shop (S corporation) projects US$340,000 of profit to the owner on a normal year; last year's tax was US$92,000, and the owner's salary withholding is set in January to cover the projected total across the crew's biweekly payrolls. March: US$210,000 of deposits arrive on the spring signings — booked as customer liabilities in the job-cost system, with 6.5% of every receipt reserved; the bank balance looks like a windfall and the profit projection doesn't move. April–May: a US$140,000 container of quartz and the fabrication payroll consume the deposits — the slabs go to inventory, consumed as jobs are cut. October: a CNC saw-jet (US$285,000) is placed in service and expensed under bonus depreciation — the fall recompute shows the year's taxable profit at about US$90,000 rather than US$340,000, and the December payroll's withholding is cut sharply, with the reserve's surplus applied to the CNC loan's first payments; the shop's alternative of placing the machine in service in January would have pushed the write-off into next year, and the owner chose this year with the recompute in hand. December: the rack count — 44 slabs and remnants at US$78,000 — sets cost of goods sold at slabs consumed, not slabs bought. His competitor paid the prior-year safe harbor's installments through September, bought a CNC in November, skipped the recompute, and overpaid the year by the tax on US$285,000 — refunded the following May, after a winter of paying interest on the loan the refund would have covered.

Official sources

The IRS explains that "individuals, including sole proprietors, partners, and S corporation shareholders, generally have to make estimated tax payments if they expect to owe tax of $1,000 or more when their return is filed," and that the penalty is avoided if they "paid at least 90% of the tax for the current year, or 100% of the tax shown on the return for the prior year, whichever is smaller" (110% if prior-year AGI exceeded $150,000). — Internal Revenue Service, Estimated taxes, https://www.irs.gov/businesses/small-businesses-self-employed/estimated-taxes

Publication 946 states that "this publication explains how you can recover the cost of business or income-producing property through deductions for depreciation (for example, the special depreciation allowance and deductions under the Modified Accelerated Cost Recovery System (MACRS))," and covers the section 179 election and its limits. — Internal Revenue Service, Publication 946, How To Depreciate Property, https://www.irs.gov/publications/p946

Practitioner note

A countertop shop's estimated taxes have three ways for cash to lie about profit — deposits before the cut, slabs before the deduction, and a CNC that erases a quarter — and the installments have to be computed on job-cost profit with the rack count and the equipment plan in view. Our fabrication clients reserve a margin-calibrated share of every receipt and run the fall recompute before any machine is placed in service, because the shop that pays the safe harbor blindly through a CNC year has lent the government the equipment loan's interest for twelve months.

See also: For related guidance, see the countertop shop's deduction guide; and browse every small business tax guide, by situation.

Next step

Fairlight Accounting is a cross-border accounting and tax practice with a U.S. Tax Desk and a Canadian Tax Desk. Our U.S. Tax Desk handles estimated-tax planning for countertop and equipment-heavy fabrication shops — deposit and slab-inventory bookkeeping, safe-harbor and annualized computations for the remodel cycle, S corporation withholding through the crew payroll, and the fall recompute for equipment placed in service. See pricing or book a call.