Small Business Tax Preparation Checklist for 2025 Returns
2025 Key Tax Dates to Know
Before diving into the checklist, bookmark these deadlines for tax year 2025 (returns filed in 2026):
| Entity Type | Form | Filing Deadline | Extension Deadline |
|---|---|---|---|
| S-Corporation | Form 1120-S | March 16, 2026 | September 15, 2026 |
| Partnership / Multi-Member LLC | Form 1065 | March 16, 2026 | September 15, 2026 |
| C-Corporation | Form 1120 | April 15, 2026 | October 15, 2026 |
| Sole Proprietor / Single-Member LLC | Schedule C (Form 1040) | April 15, 2026 | October 15, 2026 |
Q4 2025 Estimated Tax: January 15, 2026
2025 Updated Tax Limits and Thresholds
These figures change annually. Here are the 2025 numbers you need:
Standard deduction (for pass-through entities / Schedule C):
- Single: $15,000 (up from $14,600 in 2024)
- Married Filing Jointly: $30,000 (up from $29,200 in 2024)
Retirement contribution limits:
- 401(k) employee contribution limit: $23,500 (up from $23,000 in 2024)
- 401(k) catch-up (50+): $31,000 total (regular + $7,500 catch-up)
- SEP-IRA: 25% of compensation, up to $70,000
- SIMPLE IRA: $16,500 employee contribution
- IRA (Traditional/Roth): $7,000 ($8,000 if 50+)
Self-employment tax: 15.3% on net earnings (12.4% Social Security on first $176,100, plus 2.9% Medicare on all earnings). Half of SE tax is deductible.
Qualified Business Income (QBI) deduction:
- Applies to pass-through entities (S-Corps, LLCs, partnerships, sole props)
- Up to 20% of qualified business income
- Phase-out begins at $197,300 (single) and $394,600 (married) for certain service businesses
Section 179 expensing limit: $1,220,000 in 2025 (the 2026 limit is expected to be higher — check IRS.gov for the current figure)
Bonus depreciation: 40% for 2025 (down from 60% in 2024 and 80% in 2023)
Meals deduction: 50% for business meals with documented business purpose. Note: Business entertainment (concerts, sports, etc.) remains non-deductible.
What to Gather: The Complete Checklist
Business Income Documents
- ☐ All 1099-NEC and 1099-MISC received (from clients who paid you $600+)
- ☐ 1099-K from payment processors (Stripe, PayPal, Square)
– Note: 1099-K threshold for 2026 is $600 — the final phase-in threshold has arrived
- ☐ Shopify, Amazon, Etsy, or other marketplace settlement reports
- ☐ Business bank statements (all 12 months, all accounts)
- ☐ Records of any other business income (rental income, royalties, etc.)
Expense Documentation
- ☐ Business credit card statements (all 12 months)
- ☐ Receipts for all major purchases over $75
- ☐ Payroll reports and W-3 (if you have employees)
- ☐ Contractor payments made (1099-NEC must be issued for contractors paid $600+)
- ☐ Rent or lease payments with documentation
- ☐ Business insurance premium statements
- ☐ Professional service invoices (accounting, legal, consulting)
- ☐ Software subscription records (annual summary preferred)
- ☐ Vehicle mileage log (if claiming vehicle expenses)
– 2026 standard mileage rate: 71 cents per mile for business
Payroll and Employment
- ☐ W-2s issued to all employees
- ☐ W-3 transmittal form
- ☐ 941 filings (quarterly payroll tax returns)
- ☐ State payroll tax returns
- ☐ 1099-NEC for contractors paid $600+
- ☐ W-9s collected from all contractors
Assets and Depreciation
- ☐ List of all asset purchases in 2025 (with purchase date, cost, and description)
- ☐ Prior year depreciation schedule (your accountant will have this)
- ☐ Records of any assets sold, traded, or retired
Retirement and Benefits
- ☐ Solo 401(k) or SEP-IRA contribution documentation
- ☐ Employer 401(k) contributions made on behalf of employees
- ☐ Health insurance premium payments (if deducting as self-employed health insurance)
- ☐ HSA contributions and distribution statements
Home Office (If Applicable)
- ☐ Total square footage of home and dedicated office space
- ☐ Total rent paid (or mortgage interest + property taxes)
- ☐ Utilities total for the year
- ☐ Homeowner’s/renter’s insurance
R&D and Technology (SaaS/Tech Companies)
- ☐ Documentation of qualified R&D activities and employees
- ☐ Time allocation records (what percentage of engineer time was on qualifying R&D)
- ☐ Cloud infrastructure costs for development environments
- ☐ Third-party R&D contracts
Multi-Entity and Complex Situations
- ☐ SAFE note and convertible note documentation (for startups)
- ☐ Cap table with all grants, exercises, and vesting events
- ☐ Foreign bank account balances (FBAR required if over $10,000 at any point)
- ☐ Foreign income documentation (GILTI, Subpart F if applicable)
2025 Key Changes to Know Before Filing
Section 174 R&D amortization (still in effect): Research and development costs incurred in the US must be amortized over 5 years (15 years for foreign R&D) rather than immediately expensed. This rule, which took effect for tax years beginning after December 31, 2021, continues to be in force. Monitor for any legislative changes — Congress has attempted to repeal it.
1099-K threshold: The IRS is phasing in a lower threshold for Form 1099-K. For 2025, the threshold is $2,500 (transactions through payment processors like Stripe, PayPal, Venmo Business). Expect to receive more 1099-Ks than in prior years.
Bonus depreciation step-down: Bonus depreciation continues to step down — 40% in 2025, 20% in 2026, 0% in 2027 and beyond (under current law). Front-load major equipment purchases while the deduction is still meaningful.
Retirement plan contributions: The 2025 contribution limits listed above are higher than 2024 — max out if you can. SEP-IRA contributions can be made up to the filing deadline (including extensions) for the prior tax year.
Before You File: Key Review Items
- ☐ Reconcile all bank and credit card accounts — every transaction accounted for
- ☐ Review year-end accounts receivable — are all invoices either collected or written off?
- ☐ Review year-end accounts payable — are all bills recorded?
- ☐ Update your fixed asset schedule for any purchases or disposals
- ☐ Confirm all 1099s issued to contractors for 2025 (due January 31, 2026)
- ☐ Verify your corporate minutes are current (required for C-Corps and S-Corps)
- ☐ Check whether your entity election is still optimal (LLC → S-Corp analysis)
Working with Your Tax Professional
Send your tax professional:
- Clean, reconciled financial statements (P&L and balance sheet)
- Prior year tax return for reference
- This checklist with all supporting documents
- Any significant business events from the year (new entity, acquisition, real estate purchase, major asset sales)
- Questions or areas of concern early — not the week of your filing deadline
The earlier you engage your accountant, the better the outcome. Last-minute filing leads to missed deductions and stressed accountants.
Frequently Asked Questions
We filed an extension — what do we actually need to do before the October deadline?
An extension gives you more time to file — not more time to pay. If you owed taxes, interest has been accruing since April 15 on any unpaid amount. Before your October 15 extended deadline: gather all outstanding documents (particularly K-1s from partnerships or S-corps, which must be issued by their extended deadline of September 15), complete your return with your accountant, and submit. If you extended because you were waiting on K-1s, confirm those entities actually extended — some pass-through entities file on time (March 15), which means their K-1s may already be available. Common mistake: paying your extension estimate too low and being surprised by a large balance due plus interest at October filing.
Our revenue was dramatically higher than last year and we didn't adjust quarterly estimated taxes. Are we going to owe penalties?
Potentially, but the safe harbors protect you in many situations. You avoid underpayment penalties if you paid at least: (1) 100% of your prior year tax liability (110% if prior year AGI exceeded $150K), OR (2) 90% of your current year tax liability. The prior-year safe harbor is your friend if income grew unexpectedly — if you matched last year’s tax payments even though this year’s income is much higher, you’re protected from penalties on the shortfall. However, you’ll still owe the remaining tax plus interest from the original due date. For next year: when Q1 looks materially better than budget, adjust your Q2 estimate immediately rather than waiting to catch up in Q4.
We converted from a single-member LLC to an S-Corp mid-year. How does that affect our return?
A mid-year S-Corp election typically means filing in two phases: an individual Schedule C (or partnership return if multi-member) for the pre-election period, and an S-Corp return (1120-S) for the post-election period through year-end. The S-Corp election is effective from the date approved by the IRS, not the date you applied. Make sure your payroll reflects reasonable compensation from the S-Corp effective date forward — retroactive payroll corrections are administratively painful. This is one of the more complex filing situations and requires an accountant who specifically understands S-Corp elections, reasonable compensation requirements, and the mid-year partial-year P&L allocation.
We had a really bad year and have a significant net operating loss. How does that work?
Net operating losses (NOLs) from 2018 and later (under TCJA rules) carry forward indefinitely and can offset up to 80% of taxable income in future years. So if you lose $500K in 2025, you can carry that forward and offset up to 80% of any future profitable year’s taxable income. You cannot carry 2018+ NOLs back (with limited exceptions for certain farming losses). For planning purposes: if you expect to be profitable next year, the NOL carryforward will reduce your tax, but you’ll still owe some tax (due to the 80% cap). Model this when projecting cash needs — founders often assume an NOL carryforward means zero tax in the first profitable year, which is incorrect.
We paid a large insurance premium in Q4 that covers the following year. When do we deduct it?
For cash-basis taxpayers, the general rule is that prepaid expenses covering more than 12 months must be amortized — deduct only the portion that applies to the current year. However, the IRS ’12-month rule’ provides an exception: if a payment creates a benefit that doesn’t extend more than 12 months AND doesn’t extend beyond the end of the tax year following the year of payment, you can deduct the full amount in the year paid. A November 2025 payment for coverage through October 2026 (12 months) qualifies under this exception — you can deduct the full premium on your 2025 return. A November 2025 payment for coverage through November 2027 (two years) would not qualify and must be prorated.