Business Tax Filings
Done-for-you tax preparation and filing for partnerships, S-corps, C-corps and LLCs. Portside keeps you compliant and find every deduction and credit available.
Best for: Partnerships (Form 1065) · S Corporations (Form 1120-S) · C Corporations (Form 1120) · Multi-member LLCs
What's included
All tax services provided by an IRS-licensed Enrolled Agent (EA), with 12+ years of tax filing experience.
IRS Form 1065, 1120-S, or 1120 - plus one state business tax return - all at one bundled cost.
If your state requires you to file an Annual Report for your LLC or Corporation, we'll handle it with your tax filings.
Complimentary audit protection with a $1 million guarantee from Protection Plus is included with every tax return package.
All return packages include a prerecorded video walkthrough from your tax advisor, with a simple explanation of your returns.
Review of your last tax return to ensure no missed deductions or credits and confirm you didn't overpay.
Portside will monitor your business account at the IRS for any unexpected changes throughout the year.
If you receive a tax notice throughout the year, Portside will help you respond.
See everything included (2 more)
24/7 access to our secure client portal to communicate with your tax advisor and access tax documents at any time.
Maintain access to your licensed tax advisor throughout the year for questions and advice.
How it works
A short online intake form and a price quote up-front.
Your advisor handles it and reaches out if needed.
You get your finished work, with support after.
Common questions about this service
What types of businesses does Portside not serve for tax filing?
Portside serves service-based businesses only. We do not serve businesses whose chief business is to sell or manufacture products.
Can I bundle tax filing with bookkeeping and payroll?
Yes. Business Tax Filings pair with Bookkeeping + Accounting and Payroll Services (we are a Gusto payroll partner) for full back-office support from Portside.
Does Portside handle S-Corp (1120-S) filings for businesses outside North Carolina?
Yes. Portside is 100% virtual and serves clients nationwide, and we prepare Form 1120-S for S corporations.
When are business tax returns due, and can they be extended?
For calendar-year businesses, partnership (Form 1065) and S corporation (Form 1120-S) returns are due on March 15, and C corporation (Form 1120) returns are due on April 15. When a due date falls on a weekend or legal holiday, it moves to the next business day. For the 2026 tax year, that means March 15, 2027 for partnerships and S corporations, and April 15, 2027 for C corporations.
Form 7004 requests an automatic six-month extension to file. Businesses with a fiscal year follow the same pattern, counted from the end of their tax year: the 15th day of the 3rd month for Forms 1065 and 1120-S, and the 15th day of the 4th month for Form 1120. See the IRS's Publication 509 for the full tax calendar.
Do I have to meet live with someone, or schedule an appointment?
Not at all, but rest assured a human is on the other side working on your return.
Our process is designed to be fully asynchronous. All communication happens through your secure portal, and you’ll receive a personalized video reviewing your return. You can also ask questions directly in the portal's chat and we respond live during business hours.
Ready to learn more & get started?
Share a few details and Portside will take it from there.
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More about this service
Entity types Portside supports
Portside prepares business tax returns for LLCs, partnerships, S-corps and C-corps.
Tax forms Portside files
Portside supports filing of IRS Form 1065 (partnerships), IRS Form 1120-S (S-corporations), and IRS Form 1120 (C-corporations). Portside also file IRS Form 990 series tax returns for nonprofit organizations, and IRS Form 1040 tax returns for individuals with Schedule C businesses. Portside will also file any corresponding state tax returns, with one state filing included in each business tax return package (2+ states are an additional per-state fee).
Who this is not for
Portside does not serve businesses whose chief business is to sell or manufacture products. We work with service-based businesses only.
Why work with an Enrolled Agent
Your return is prepared by an IRS-licensed Enrolled Agent, and a QuickBooks ProAdvisor. Portside has served numerous clients and filed even more tax returns, all 100% virtually.
Related Portside guides
- Understanding Schedule K-1 for Partnership Income
- C-Corp vs. S-Corp: Which Should You Choose?
- Why Reliable Bookkeeping Matters for Your Business
- Why Quickbooks Online is Right for your Business