Baltimore business owners have to juggle federal and Maryland state deadlines that do not always line up. Miss one and the penalties from the Comptroller of Maryland add up quickly. This is the single calendar we hand every Maryland small business client at the start of the year. Print it, pin it to your wall, or copy it into your calendar app.
Everything below assumes calendar-year filing. If your fiscal year is different, shift the state dates that reference year-end accordingly and talk to your CPA about the federal ones.
The recurring monthly and quarterly rhythm.
Before we hit the specific dates, two habits every Maryland business should build into the monthly rhythm:
- Sales & Use Tax is filed with the Comptroller of Maryland monthly for most retailers, generally due by the 20th of the following month. If your gross sales are under certain thresholds, you may be assigned quarterly or annual filing instead. Check your bFile account for your assigned frequency.
- Withholding tax on employee wages is remitted based on your assigned frequency (accelerated, monthly, or quarterly). Most small employers file monthly. Late remittance triggers penalties fast.
Quarter 1 (January to March).
January 15
Federal & Maryland Q4 2025 estimated tax payment. Individuals, sole proprietors, and pass-through owners pay their fourth-quarter 2025 estimated tax to both IRS and Comptroller of Maryland.
January 31
W-2s and 1099-NECs. Deliver to recipients and file with SSA/IRS. Maryland W-2 copies also go to the Comptroller. If you missed a contractor payment for classification, this is the fire drill nobody wants.
February 20
Maryland Annual Report and Personal Property Return. Every Maryland entity (LLC, Corporation, LP) files this with the State Department of Assessments and Taxation (SDAT). Filing fee is $300 for most entities. There is no grace and no fun way to catch up if you miss it.
The Personal Property Return (Form 1) is what determines your Baltimore City or County personal property tax. If your business owns computers, furniture, or inventory in Maryland, you file it.
March 17
S-Corp and Partnership federal returns due (Form 1120-S and Form 1065). Also Maryland Form 510 (Pass-Through Entity Income Tax Return) is due. If you elected the Maryland PTE tax, this is where it gets reconciled.
If you cannot file on time, this is also the deadline to request a six-month extension. Extensions are for filing, not paying — estimated tax must still be paid by this date.
Not sure your books are ready for these deadlines?
See the sample monthly reporting package we deliver to Maryland small business clients. Clean P&L, balance sheet, and a tax-ready summary your CPA will thank you for.
Get the sample packageQuarter 2 (April to June).
April 15
Federal individual and C-Corp returns. Form 1040 (personal), Form 1120 (C-Corp), and Maryland Form 502 (individual) and Form 500 (corporate) all due on the same day.
Q1 2026 estimated tax payment. Both federal and Maryland state.
This is the single most concentrated day on the entire calendar. Every small business owner in Baltimore feels this one. If your books are still open on this date, the fire drill is not fixable in one day.
June 15
Q2 2026 estimated tax payment due for both federal and Maryland state. Note this is only two months after Q1, not three — the estimated tax quarters are not equal thirds of the year.
Quarter 3 (July to September).
July 31
Federal Form 941 for Q2 (quarterly payroll tax return) due. Maryland MW-506 for state withholding on the same cadence.
September 15
Extended S-Corp / Partnership returns due if you filed for an extension in March.
Q3 2026 estimated tax payment for federal and Maryland state.
Quarter 4 (October to December).
October 15
Extended individual and C-Corp returns if you filed an extension in April.
October 31
Federal Form 941 for Q3 (quarterly payroll return) and Maryland MW-506.
December 31
Year-end. Last day to make deductible expenses for the current tax year, fund SEP or Solo 401(k) contributions (Solo 401(k) contribution technically must be initiated by year-end, though the funding can happen later), and take any last-minute tax moves. It is also the last chance to buy equipment and take Section 179 depreciation for the current year.
Two Maryland-specific traps that catch out-of-state owners.
1. Baltimore City has a separate personal property tax filing. The Maryland Personal Property Return you file in February is used by Baltimore City (and every Maryland county) to assess personal property tax on your business assets. Baltimore City rates are different from Baltimore County. If you moved offices across the city line, your rate changed.
2. Maryland PTE election. If your entity is a pass-through (LLC, S-Corp, Partnership), Maryland allows you to elect to pay income tax at the entity level (called the PTE election). This can be a meaningful federal deduction for owners since the SALT cap does not apply to entity-level state taxes. The election is annual and must be made in a timely fashion. Talk to your CPA about whether it makes sense for your situation before the return is filed.
How we help.
At RS Accounting & Bookkeeping we run monthly closes for Maryland small businesses on this exact calendar. Every deadline is on our internal tracker before it hits yours. We prep tax-ready packages that our clients hand directly to their CPAs (or to our trusted tax partner Veritax USA in Bethesda) with no scrambling in March or April.
If you are running your own books today and this list gave you a small panic attack, that is normal. It is also fixable in a couple of weeks with a proper monthly workflow.