Dental Practice Estimated Taxes: Collections That Lag Production, the Insurance Payer Mix, and the Cone-Beam Year

Dental practices meet the estimated tax system with a predictable base and two large levers. 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 — nearly every practice owner is above it) in equal installments, 90% of the current year's tax in equal installments, or the annualized method. Collections, not production: a practice's production (the fees for the procedures performed) is not its income; collections are — the amounts actually received from insurers (net of the contractual write-off between the fee schedule and the allowed amount) and from patients (co-pays at the visit, balances billed after the insurer adjudicates, and financed treatment plans paid by the financing company at the visit less the dealer fee) — so under the cash method (most practices), income is the collections as they arrive, and a practice's collections in a month are the production of the prior thirty to sixty days for insured patients (the claim cycle — submission, adjudication, payment) and the same day for fee-for-service and financed patients; the projection runs on collections from the practice management system's reports, and the payer mix (the share of production that is fee-for-service, PPO, Medicaid, or financed) sets both the collection ratio (fee-for-service near 100 percent of fees; PPO at the contracted allowance — 60 to 80 percent of fees; Medicaid lower) and the lag. The base: patients come in every week — a hygiene recall schedule fills the hygienists' columns months ahead, and restorative and specialty production follows the exams — so a practice's monthly collections are the steadiest in the professional trades, with a January dip (deductibles reset — patients defer), a year-end push (patients using remaining annual maximums — November and December production runs high, collected in December and January), and the summer's slower elective work; equal installments fit, and the S corporation's salary withholding (below) is the mechanism nearly every practice uses. The equipment lever — the cone-beam year: a practice that adds cone-beam imaging, a scanner and milling unit, or a new operatory's chairs in a year expenses six figures under section 179 and bonus depreciation (the dental deductions guide) — cutting the year's taxable profit by the equipment's cost against a collection year that looks normal; a practice that runs the prior-year safe harbor's withholding through September and takes delivery in October has over-withheld by the tax on the write-off, and the fall recompute adjusts the December payroll's withholding (or the fourth installment) — the purchase's timing (placed in service in December versus January) is decided with the estimated-tax picture and the practice's cash in view, and a practice financing the equipment has the loan's payments to fund from the tax saving. The retirement lever — the December decision: the owner's 401(k) profit-sharing contribution and the cash balance plan's contribution (the dental entity guide — six figures for a high-earning owner) are deductible for the year if made by the return's due date (with extensions) — but the plan need not exist by year-end (under the SECURE Act, a new cash balance or profit-sharing plan adopted by the return's due date, with extensions, is treated as adopted on the last day of the year — only the 401(k)'s salary deferrals need a plan in place during the year, apart from SECURE 2.0's first-year exception for a sole proprietor's solo 401(k)), the contribution is computed on the year's compensation (the owner's W-2 salary, set through the year), and the actuary's required contribution range is known in the fall; the fall recompute sets the year's contribution and therefore the year's taxable profit, and the December payroll's withholding is set for it; a practice owner who decides the contribution in April has the deduction but not the withholding alignment — the tax was over-withheld through December and comes back as a refund. The S corporation practice (the entity guide): the owner's salary withholding — through the staff's biweekly payroll, always in place — covers the tax on salary and projected distributions, deemed paid evenly across the year regardless of when withheld; the January W-4 is set from the projection (collections, the equipment plan, the retirement plan's expected contribution), the fall recompute adjusts it for the equipment placed in service and the actuary's figure, and the December payroll cures the year — the practice owner rarely files a Form 1040-ES. The multi-dentist practice: an S corporation's shareholder-dentists each run their withholding through their own salary (each's production and share of profit projected); a partnership's partner-dentists estimate on their guaranteed payments and distributive shares with nothing withheld — the reserve on each distribution, and the state's pass-through entity tax election where available (an entity-level payment on its own schedule). What the estimate includes: federal income tax on projected profit (collections less the practice's costs — supplies and lab at their percentages, staff, occupancy, compliance, insurance); no self-employment tax for an S corporation owner (payroll tax on the salary instead) — self-employment tax on a partnership dentist's guaranteed payment and share; the state's estimates (and the pass-through entity tax); the QBI deduction — zero for most practice owners above the range (the entity guide), so not in the projection; the retirement plan's contribution (the largest adjustment); the equipment write-offs (the second); the real estate LLC's rent (a cost to the practice, income to the LLC — projected on both sides); and the Additional Medicare Tax on the salary above the threshold (withheld through payroll above US$200,000 automatically; the owner's total household wages may push the 0.9 percent higher than the practice's withholding captured — a Form 8959 item). The quarterly check: collections against the projection by payer (the practice management system's reports — collection ratio, days in accounts receivable, the insurance aging); production trends (the year-end maximums push); the equipment plan; the retirement plan's expected contribution (the actuary's fall range); profit through the quarter annualized against the withholding; and the W-4 adjustment. The failure modes: projecting on production (over-projecting by the write-offs and the lag); running the prior year's withholding through a cone-beam year (over-withheld, refunded in the spring — a year of interest on the equipment loan); deciding the retirement contribution in April instead of the fall (the deduction without the withholding alignment); the December production push collected in January projected as December income; and the partner-dentist with no reserve on distributions meeting a large April balance. The calendar: January — last year closed (collections by payer reconciled, the retirement contribution finalized by the return's due date, the equipment placed in service), the W-4 set from the projection (collections, equipment plan, expected plan contribution); quarterly — the check on collections and the payer mix; October — the fall recompute (equipment placed in service, the actuary's figure, the year-end production push, the rent on both sides) and the December W-4; December — the final payroll's withholding cure and the retirement plan's establishment if new; filing — the plan contribution made by the due date, Form 8959.

Key takeaways

• Estimate on collections, not production — the contractual write-offs never arrive, and insured production is collected thirty to sixty days later at the payer's allowed amount; the payer mix sets the collection ratio and the lag.
• The base is the steadiest in the professional trades (recall schedules fill the columns months ahead), with a January dip and a year-end maximums push collected into January.
• Two six-figure levers move the year: the equipment placed in service (recompute in the fall; December versus January placement is a decision) and the retirement plan contribution (set in the fall from the actuary's range so the December withholding matches — not decided in April).
• S corporation owners run everything through salary withholding on the staff's payroll — deemed paid evenly, set in January, adjusted in October, cured in December; partner-dentists reserve on every distribution.
• The QBI deduction is not in most practice owners' projections (zero above the range); the Additional Medicare Tax and the real estate LLC's rent on both sides are.

The dental practice's estimated-tax calendar

January: last year closed (collections by payer; plan contribution by the due date); W-4 from the projection (collections, equipment plan, expected contribution). Quarterly: collections by payer; collection ratio; A/R aging; production trend; equipment plan; actuary's range. October: fall recompute — equipment placed in service, actuary's figure, year-end push, rent both sides; December W-4. December: final payroll cure; new plan established if needed. Filing: contribution by due date; Form 8959. The two levers — equipment and the plan — are the whole recompute.

Worked example

A solo general practice (S corporation, staff of nine) projects US$480,000 of profit on US$2.1 million of collections (US$2.6 million of production, a 62/38 PPO/fee-for-service mix, a 30-day average lag). January: the owner's salary is US$240,000 and her W-4 is set to cover the tax on salary and a US$240,000 projected distribution, less the expected US$190,000 retirement contribution from the actuary's preliminary range. The quarterly checks: collections on projection, with the PPO collection ratio holding at 68 percent and days in A/R at 28. October recompute: a cone-beam unit (US$118,000) delivered and placed in service in September (section 179), the actuary's cash balance figure finalized at US$176,000 plus US$34,000 of 401(k) profit sharing — US$210,000 of owner contributions — and the year-end production push projected at US$260,000 of December production, half of it collected in January; the year's taxable profit projects at US$152,000 after the equipment and the plan, and the December payroll's withholding is cut to cure the year without a refund. December: the final payroll, the plan contributions scheduled for payment by the return's extended due date (September 15 — also the cash balance plan's minimum-funding deadline, 8½ months after the plan year ends), the real estate LLC's US$11,000 monthly rent on both sides of her return. Her colleague across town projected on production, ran last year's withholding through his own cone-beam year, and decided his cash balance contribution in April — a US$90,000 refund the following May, a year of interest on the equipment loan, and a plan contribution that had to be funded from a line of credit because the cash had gone to the IRS.

Official sources

The IRS states: “Generally, most taxpayers will avoid this penalty if they owe less than $1,000 in tax after subtracting their withholdings and credits, or 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.” — Internal Revenue Service, Estimated taxes, https://www.irs.gov/businesses/small-businesses-self-employed/estimated-taxes

The IRS states: “Benefits provided under the plan are limited. Deduction limit is any amount up to the plan’s unfunded current liability (see an enrolled actuary for further details).” — Internal Revenue Service, Defined benefit plan, https://www.irs.gov/retirement-plans/defined-benefit-plan

Practitioner note

A dental practice's estimated taxes run on collections that lag production by a payer's claim cycle and arrive net of write-offs that never existed as income — and on two six-figure levers the fall recompute has to catch: the imaging unit placed in service in September and the actuary's cash balance figure finalized in October. Our dental routine sets the January W-4 from the collection projection and the plan's expected contribution, recomputes in October, and cures the year in the December payroll — because the owner who decides the retirement contribution in April gets the deduction and a refund of the withholding that should have funded the plan.

See also: For related guidance, see law firm estimated taxes; 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 dental practices — collections-based projections by payer mix, S corporation withholding through staff payroll, equipment-year recomputes, retirement plan contribution timing with actuarial ranges, partner-dentist reserve rules, and Form 8959 coordination. See pricing or book a call.