Maryland business owners answer to two tax systems that look similar but behave very differently. The IRS and the Comptroller of Maryland have different rates, different deductions, different forms — and several places where Maryland deliberately breaks from federal rules. Miss the differences and you either overpay or get a letter. Here are the ones that matter.
The starting point most new business owners get wrong: filing and paying your federal taxes does nothing for Maryland, and vice versa. The IRS and the Comptroller of Maryland are separate agencies with separate payment systems, separate deadlines for some obligations, and separate enforcement. Every federal obligation — income tax, estimated payments, payroll deposits — has a Maryland counterpart that must be handled independently.
Maryland does start from your federal return — your Maryland income tax calculation begins with federal adjusted gross income — which is why the two systems feel connected. But from that starting point, Maryland adds its own layers, takes away several federal benefits, and imposes obligations that have no federal equivalent at all. Our Maryland Tax Guide covers the full compliance stack; this article focuses on where the two systems diverge.
| Tax Item | Federal (IRS) | Maryland (Comptroller / SDAT) |
|---|---|---|
| Individual income tax | Brackets from 10% to 37% | 2% to 5.75% state — PLUS a county local tax (Frederick County: tiered, up to 3.2%) |
| Corporate income tax | Flat 21% | Flat 8.25% |
| QBI deduction (20% pass-through deduction) | Yes — Section 199A | No — provides no Maryland benefit |
| Bonus depreciation | 100% under current law | Decoupled — Maryland requires an addback and separate depreciation |
| SALT deduction workaround | Deduction capped at individual level | PTE entity-level election available |
| Sales tax | None | 6% general / 9% alcohol |
| Business personal property tax | None | Annual SDAT filing + county tax on business assets |
| Estimated payments | Quarterly to IRS | Separate quarterly payments to the Comptroller |
| Payroll | 941 deposits, FUTA | MW506 withholding + BEACON unemployment insurance |
Everyone knows the federal brackets. What surprises new Maryland business owners is the second state layer: every Maryland county imposes its own local income tax on residents, collected through the state return. Frederick County uses tiered local rates topping out at 3.2% — which, stacked on Maryland's 5.75% top state rate, produces a combined top marginal state burden near 8.95% before a dollar of federal tax.
For pass-through business owners, that combined rate applies to business profits flowing onto the personal return. It's also why Maryland-specific planning — the PTE election, retirement plan contributions, equipment timing — carries roughly an extra 9 cents of value per dollar beyond the federal savings.
Maryland deliberately refuses to follow — "decouples from" — several federal provisions. These are the differences that produce genuinely different numbers on your two returns:
The federal Qualified Business Income deduction lets many pass-through owners deduct 20% of business income federally. Maryland provides no equivalent — because the QBI deduction is taken after adjusted gross income, and Maryland's calculation starts from AGI, the deduction never reaches your Maryland return. A business owner in the QBI sweet spot can face a meaningfully different effective rate federally versus in Maryland on the same income.
Federal law currently allows 100% bonus depreciation on qualifying equipment. Maryland decouples: bonus depreciation claimed federally must be added back on the Maryland return (via the decoupling modification, Form 500DM for entities), with the asset depreciated for Maryland purposes under regular schedules instead. The result is that a big equipment write-off shrinks your federal income immediately while your Maryland income stays higher in year one — and the difference reverses over the asset's life. Maryland does generally conform to Section 179 expensing, which makes 179-versus-bonus a genuine planning decision in this state, not an interchangeable choice.
This is the single most common preparation error we see on self-prepared and out-of-state-prepared Maryland business returns: the federal depreciation number carried straight onto the Maryland return with no decoupling modification. It understates Maryland income in year one — and when the Comptroller catches it, the assessment comes with interest.
The federal standard deduction is large. Maryland's is small — 15% of Maryland AGI, capped at a few thousand dollars ($2,700 single / $5,450 joint region, indexed). And Maryland only allows you to itemize if you itemized federally. The combination means many taxpayers who happily take the big federal standard deduction get a comparatively tiny Maryland deduction with no way to itemize around it — one more reason the effective Maryland burden is heavier than the rate table alone suggests.
One place Maryland actively helps business owners: the pass-through entity tax election. S-Corps and partnerships can elect to pay Maryland income tax at the entity level, converting a capped individual SALT deduction into an uncapped federal business deduction, with owners receiving a Maryland credit to prevent double taxation. With the SALT cap raised to $40,000 through 2029 (and scheduled to revert after), whether the election pays depends on your numbers — we cover when the election pays as part of our S-Corp and entity analysis.
Several Maryland obligations simply don't exist at the federal level, which is exactly why owners who "handle taxes" through national software miss them:
Self-employed owners and pass-through business owners owe quarterly estimated payments to both systems — IRS Direct Pay and the Comptroller's portal are entirely separate, with separate safe harbor rules (Maryland's is 110% of prior-year tax or 90% of current-year). Paying one does not credit the other, and each system calculates its own underpayment penalty independently. Our Maryland estimated payments guide covers the mechanics.
The two systems reconnect at the end: if the IRS audits you and adjusts your federal return, Maryland requires you to report the federal changes to the Comptroller within 90 days of the final federal determination. The Comptroller also receives information from the IRS directly, so unreported federal adjustments eventually surface — with Maryland tax, interest, and penalties attached. The same logic applies in reverse for amended returns: a federal amendment that changes AGI almost always requires a Maryland amendment too.
How we handle the two-system problem for clients: every return we prepare is built with both systems in view — decoupling modifications calculated, PTE election analyzed, both sets of estimated payments scheduled, and every Maryland-only obligation (SDAT, personal property, sales tax, BEACON) tracked on one calendar. The gap between federal and Maryland rules is exactly where a Maryland-based CPA earns their fee over national software. Our tax planning services and small business tax team work both sides of the ledger.
We'll review your federal and Maryland returns side by side — decoupling modifications, PTE election, and every Maryland-only filing — and show you what's been missed. Call (301) 662-6992.
Book a ConsultationOnly partly. Maryland starts from federal AGI, but then applies its own additions and subtractions — including the bonus depreciation addback and the loss of the QBI benefit. Software handles this correctly only when the Maryland-specific screens are completed, which is precisely where self-prepared returns go wrong.
Yes — Maryland decouples from federal bonus depreciation, so the federal deduction is added back and the truck is depreciated for Maryland purposes over its regular schedule. You still get the full deduction in Maryland over time, just not all at once. Since Maryland generally conforms to Section 179, choosing 179 over bonus can keep the two returns aligned — which is a planning conversation to have before the purchase.
Not quite — Maryland requires you to report the federal changes within 90 days of the final determination, and the Comptroller will eventually receive the adjustment data from the IRS regardless. Reporting promptly limits the interest; waiting for Maryland to find it adds penalties.
Both, together. The federal stakes are bigger per dollar, but Maryland's combined rate near 9% is too large to ignore, and several strategies — the PTE election, 179-versus-bonus, retirement contributions — play out differently in each system. The right plan is optimized across the two, not for either one alone.
By Roy Cogliandolo, CPA · Mercer Flanagan · February 3, 2026
This article is general information, not tax or legal advice. Rates, caps, and conformity rules change — verify current-year treatment with a qualified professional before acting.