Alabama’s corporate income tax is a flat 6.5% levy on the net income a C corporation apportions to the state, and the return is due one month after the corresponding federal deadline. It reaches corporations organized in Alabama and out-of-state corporations that do business in or earn income from Alabama sources. S corporations with a valid federal election are not subject to the 6.5% rate; their income passes through to shareholders, though they still file an Alabama informational return.
Who Has to File
Two groups owe the tax: any corporation domiciled in Alabama, and any corporation doing business in or earning income from Alabama sources, including income from property located in the state.1Alabama Legislature. Alabama Code 40-18-2 – Levied; Persons and Subjects Taxable Being licensed or qualified to transact business in Alabama counts as doing business, even in a year with minimal activity.
Out-of-state corporations without an Alabama office or employees are measured against a factor-presence nexus standard. Exceeding any one of these thresholds during the tax period triggers a filing obligation:2Alabama Legislature. Alabama Code 40-18-31.2 – Factor Presence Nexus Standard for Business Activity
- $50,000 in real or tangible personal property owned or rented in Alabama
- $50,000 in Alabama payroll
- $500,000 in sales sourced to Alabama
- 25% or more of total property, payroll, or sales located in Alabama
Owned property counts at original cost; rented property is valued at eight times the net annual rent. A single threshold is enough.
How the Tax Is Calculated
The rate is a flat 6.5% of taxable income apportioned to Alabama, with no brackets.3Alabama Legislature. Alabama Code 40-18-31 – Corporate Income Tax Two features shape what the corporation actually pays.
Deduction for Federal Income Tax Paid
Alabama is one of a small number of states that allow corporations to deduct federal income taxes paid when calculating state taxable income.4Alabama Legislature. Alabama Code 40-18-35 – Deductions Allowed For a multistate corporation, the deductible portion is limited to the share matching the ratio of Alabama taxable income to total taxable income everywhere. The deduction can meaningfully lower the effective state rate, and overlooking it is a common mistake on Alabama returns.
Apportionment for Multistate Corporations
A corporation with income earned inside and outside Alabama apportions to the state using a single-sales-factor formula for tax years beginning on or after January 1, 2021.5Alabama Administrative Code. Alabama Administrative Code Rule 810-27-1-.09 – Apportionment Formula The percentage of total sales sourced to Alabama sets how much income the state can reach. This replaced the older three-factor formula that also weighted property and payroll, and it tends to favor corporations with significant Alabama property and employees but relatively fewer in-state sales.
When the Return Is Due
Form 20C is due one month after the corresponding federal due date. For a calendar-year C corporation, the federal return is due April 15 and the Alabama return is due May 15. Fiscal-year corporations follow the same rule: the 15th day of the fifth month after the close of the fiscal year, so a June 30 year-end produces an October 15 due date.6Alabama Department of Revenue. Due Dates
Alabama automatically extends its filing deadline to match any federal extension, plus the same one-month cushion. A calendar-year corporation with a federal extension to October 15 has until November 15 to file the Alabama return.7Alabama Department of Revenue. Corporate Income Due Date – Extensions The federal extension form must be submitted with the Alabama return when it is filed.
An extension to file is not an extension to pay. The full liability is due on the original due date (May 15 for calendar-year filers), and underpayment on that date triggers penalties and interest even when the return itself is timely under the extension.
Quarterly Estimated Payments
A corporation whose Alabama income tax liability will reach $500 or more for the year must make quarterly estimated payments.8Alabama Department of Revenue. Does Alabama Require Quarterly Estimated Tax Payments? Installments fall on the 15th day of the 4th, 6th, 9th, and 12th months of the tax year. For calendar-year filers that means April 15, June 15, September 15, and December 15.
Skipping an installment or underpaying draws an underpayment penalty on top of any year-end balance. For corporations with variable income, safe-harbor payments based on the prior year’s liability are the simplest way to avoid that exposure.
Consolidated Returns for Affiliated Groups
An affiliated group filing a federal consolidated return may elect to file an Alabama consolidated return for the same year.9Alabama Legislature. Alabama Code 40-18-39 – Corporate Returns The election is the taxpayer’s choice, made by the common parent on behalf of all group members, and must be filed with the Alabama Department of Revenue by the due date (including extensions) of the first consolidated return.
Only group members with substantial nexus in Alabama are included. Each member calculates its Alabama taxable income or loss separately and applies the apportionment formula; the results are combined on Form 20C-C.10Alabama Administrative Code. Alabama Administrative Code Rule 810-3-39-.03 – Consolidated Filing The advantage is that one member’s Alabama-sourced loss can offset another member’s Alabama-sourced income.
The Business Privilege Tax Is Separate
The 6.5% income tax is not the only annual obligation. Alabama also imposes a business privilege tax on every corporation, limited liability entity, and disregarded entity organized under Alabama law or doing business in the state.11Alabama Department of Revenue. Alabama Business Privilege Tax It is calculated on net worth in tiers, uses a different form (Form CPT for C corporations), and follows the federal due date rather than the May 15 income tax date. It also continues to accrue every year until the entity is formally dissolved or withdrawn through the Alabama Secretary of State, even after operations stop. Plan for both taxes; satisfying one does not satisfy the other.
Penalties
Alabama enforces late-filing and late-payment penalties separately, and a corporation can face both at once.
- Late filing: the greater of 10% of any additional tax due with the return, or $50.
- Late payment: 1% of the unpaid tax for each month or partial month late, capped at 25%.
- Negligence: an additional 5% on the portion of any underpayment attributable to carelessness or disregard of regulations.
- Fraud: 50% on the portion of any underpayment caused by fraud.
Interest accrues on unpaid balances from the original due date. Because a filing extension does not push back the payment deadline, a corporation that files under extension but pays late owes the late-payment penalty and interest even though the return itself was timely.