Tax season lands on every founder's calendar, whether or not you started a company to deal with it. The 2027 filing season covers tax year 2026, and a missed date can cost you penalties and interest. This guide walks you through the key dates, a step-by-step filing process, and when a tax professional is worth bringing in.
TLDR:
Tax season is the time for individuals and businesses to file returns for the previous year. The return you file depends on how your company is taxed: C-corporations file Form 1120, S-corporations file Form 1120-S, partnerships and multi-member LLCs file Form 1065, and owners report their personal income on Form 1040. Federal and state obligations are separate, so a Delaware C-corp, for example, also owes a state franchise tax and annual report. Knowing which forms and deadlines apply to you helps you avoid penalties and claim any refund you're owed. Confirm the details for your situation with your CPA or tax preparer.
Staying ahead of these dates is key:
| Filing dates | Description | Relevant Forms | Official Links |
|---|---|---|---|
| February 1, 2027 | Receive W-2s and other tax documents (January 31 falls on a Sunday, so the deadline moves to the next business day) | W-2 Forms | IRS W-2 Information |
| March 1, 2027 | Delaware franchise tax and annual report due for tax year 2026 | N/A | Delaware Franchise Tax |
| March 15, 2027 | Deadline for Partnerships or Multi-Member LLCs | Form 1065 | IRS Form 1065 |
| March 15, 2027 | Deadline for S-Corporations | Form 1120-S | IRS Form 1120-S |
| April 15, 2027 | Deadline for C-Corporations | Form 1120 | IRS Form 1120 |
| April 15, 2027 | Deadline for Individual Tax Returns and Payments | Form 1040 | IRS Form 1040 |
| October 15, 2027 | Final Deadline for Extended Tax Returns | Various | IRS Tax Extensions |
| No deadline for U.S. companies | FinCEN permanently ended beneficial ownership (BOI) reporting for U.S. companies and U.S. persons. The final rule took effect August 14, 2026. Only foreign companies registered to do business in the U.S. may still need to report. | N/A | Treasury: BOI reporting ends for U.S. companies |
Missing these deadlines can trigger penalties and interest, so put them on your calendar now. When a deadline falls on a weekend or legal holiday, it moves to the next business day.
Filing taxes doesn't have to be daunting. Follow these steps for a smoother process:
If you pay contractors, collect a W-9 from each one when you onboard them, so your 1099 reporting for tax year 2026 is ready when the new year starts.
Two updates affect the paperwork you will handle in early 2027. First, the IRS now lists a $2,000 1099-NEC and 1099-MISC threshold for payments made after 2025, up from $600, with inflation adjustments starting in 2027. If you pay a contractor less than $2,000 in 2026, you generally will not file a 1099 for them in January. Second, the IRS confirmed that the Form 1099-K threshold reverted to $20,000 and 200 transactions, so fewer small sellers and payment-app users will receive that form.
Looking further ahead, the IRS has already published its tax year 2027 inflation adjustments. The standard deduction rises to $16,600 for single filers and $33,200 for married couples filing jointly, which helps if you plan your income and estimated payments a year out. Even with a higher 1099 threshold, you still report all business income and expenses on your return, so keep your books current through year-end and ask your tax professional how these changes apply to you.
With less than seven weeks left in 2026, the books you finish now decide how calm March and April feel. If you pay estimated taxes as an individual, including founders with pass-through income, the fourth payment for tax year 2026 is due January 15, 2027, according to IRS Publication 505. Corporations follow different installment dates, so confirm yours with your tax professional.
Puzzle updates your financials daily and categorizes about 90% of transactions automatically (about 85% finalized), so your year-end review is a short approval pass, not a rebuild. Puzzle does not offer tax services, so your CPA or tax preparer still handles the filing.
In certain scenarios, professional assistance can be invaluable:
Sometimes, you might need more time to file your taxes. Here's what you should know:
Further resources to ease your tax filing include:
Understanding the key dates, filing processes, and when to seek professional help can simplify your tax experience. Stay organized and informed for a successful tax season.
The main deadlines for tax year 2026 are March 15 for partnerships, multi-member LLCs, and S-corporations; April 15 for C-corporations and individual returns; and October 15 for extended returns. Delaware C-corps also face a March 1 franchise tax and annual report deadline. When a deadline falls on a weekend or legal holiday, it moves to the next business day.
The IRS raised the 1099-NEC and 1099-MISC filing threshold from $600 to $2,000 for payments made after 2025, so if you paid a contractor less than $2,000 in 2026, you generally won't file a 1099 for them in January. The 1099-K threshold reverted to more than $20,000 and more than 200 transactions. You still report all business income and expenses on your return regardless of whether a 1099 was issued.
If you own a business or have multiple income sources, a tax professional can give you tailored advice and help you avoid penalties. Major life changes such as marriage or buying a house are also good reasons to bring one in. Clean, up-to-date books going into tax season make that conversation faster.
No. A tax extension gives you more time to file your return, not more time to pay. Estimated taxes are still due by April 15. Paying late triggers interest and penalties even if your extended return is filed on time by October 15.
Collect a W-9 from every contractor at onboarding so your 1099 reporting is ready when the new year starts, and keep your books current through year-end instead of reconstructing them in April. AI-native accounting software like Puzzle updates your financials daily and automates transaction categorization, so your records are accurate before tax season starts, not scrambled together at the end.
No. Puzzle supports USD and US entities only, so it does not handle multi-currency accounting, and it does not cover accounting or tax rules outside the US (such as the UK or EU). It is built for US startups, including Delaware C-corps. If you run an international entity, keep that entity in a system built for its local requirements.
Get the books finished first, because your tax preparer needs complete financial statements to file. If you are behind, you have two options. You can catch up yourself in Puzzle, where AI categorizes about 90% of transactions automatically (about 85% finalized) and you review the results. Or you can hand it off: Puzzle's catch-up bookkeeping starts at $300 per month of books (eleven months behind is $3,300) and requires an active Puzzle software subscription. Either way, start well ahead of October 15 so your CPA has time to work. Puzzle does not offer tax services, so a CPA or tax preparer files the return.
Puzzle drafts categorization during the month and flags exceptions early, so you review the work instead of rebuilding it at period end. If you want a bookkeeper to run the close, Puzzle's Full Service tier (from $499/mo per entity, on top of a software plan) puts a named bookkeeper on your monthly close, and you approve the month. Customers who fully onboard and connect supported integrations are also eligible for a refund of subscription fees if they do not see at least a 50% reduction in month-end close time within 60 days.
You need your own CPA or tax preparer. Puzzle does not offer tax services, so it does not file returns, prepare tax packages for filing, or give tax advice. What Puzzle gives your preparer is clean, current books: a GAAP-compliant income statement, balance sheet, and statement of shareholders' equity, plus a tax package export (CSV) and 1099 vendor reporting export. Puzzle's accountants or partner firms handle your bookkeeping, and your tax professional handles the filing.
Not on its own, and Puzzle is not built to try. Puzzle's AI suite categorizes transactions automatically, and when its confidence falls below a 99% threshold it assigns no category and flags the transaction for review instead of guessing. The rest still needs a person. Founders spend about 15 to 20 minutes per week reviewing and finalizing AI-categorized transactions, and nothing is final until someone approves it. AI categorization is also transaction-level, so it will not split a mixed purchase into component categories, and accuracy on a new account starts below the typical rate until history and rules build up. For a 10-person startup, the workable setup is AI drafting the books and a human owning the approval. You can do that review yourself, or add Expert Reviewed bookkeeping (from $99/mo per entity, for setups with up to $10K in monthly expenses and no payroll processing) or Full Service (from $499/mo per entity), where a Puzzle accountant or partner firm reviews and closes the books. If you run payroll, Full Service is the likelier fit. Whichever route you pick, you remain responsible for the accuracy of your business records, so keep a human reviewer in the loop. Puzzle does not offer tax services, so your CPA or tax preparer still files the return.
It depends on how your company is taxed, so confirm the details with your CPA. C-corporations pay their own estimated federal income tax in installments due on the 15th day of the 4th, 6th, 9th, and 12th months of the tax year (April 15, June 15, September 15, and December 15 for calendar-year companies). Partnerships and S-corporations generally do not pay federal income tax at the entity level, so owners pay estimated tax on their share of income with their personal installments (April 15, June 15, September 15, and January 15 of the following year). Single-member LLCs report on the owner's individual return by default. Sales tax is set by each state, and sometimes by city or county, so registration, rates, and filing frequency vary by where you sell. Puzzle does not offer tax services or tax advice, so your CPA or tax preparer sets your payment schedule.
Tax season is one use of your books, not the reason to keep them. Puzzle updates your cash position, P&L, and balance sheet daily, and it tracks burn rate, runway, and ARR/MRR as you go. AI categorizes about 90% of transactions automatically (about 85% finalized), and founders typically spend about 15 to 20 minutes per week reviewing them. Core and above add an automated close checklist for your month-end close. For a SaaS startup, that means investor-ready statements and a live view of runway before your next fundraise. For a small business with several locations or projects, project-level P&L tracking shows which ones earn their keep. Your CPA still files the return, and the same clean books make that work faster every year.
The 2027 filing season rewards founders who plan early. Know your key dates, follow the filing steps, and bring in a tax professional if your situation is complex. Good records and an early start make for a calmer tax season. Book a demo to see how Puzzle keeps your books current all year.
