12 Small Business Tax Deductions Most Owners Miss in 2026

Format of this guide: ranked listicle with a comparison table and a decision framework. Figures apply to U.S. federal income tax only.

1. Why did the IRS change the mileage rate twice in 2026?

The IRS set the 2026 business standard mileage rate at 72.5 cents per mile in Notice 2026-10, published December 29, 2025. Then it raised the rate to 76 cents per mile effective July 1, 2026, through Announcement 2026-11, citing the rise in fuel prices. The IRS had not made a mid-year adjustment since 2022.

This means your 2026 mileage deduction uses two rates, not one:

• January 1 to June 30, 2026: 72.5 cents per mile
• July 1 to December 31, 2026: 76 cents per mile
• Charitable mileage stays at 14 cents, fixed by statute under Section 170(i)

A business that drives 6,000 miles in each half of 2026 deducts $8,910, not the $8,700 a single-rate calculation produces. On 30,000 miles the gap grows to about $525. Split your mileage log at June 30 and apply each rate separately.

2. How much can you expense under Section 179 in 2026?

For tax years beginning in 2026, Revenue Procedure 2025-32 sets the Section 179 deduction limit at $2,560,000. The phase-out starts when Section 179 property placed in service during the year exceeds $4,090,000, and the deduction drops dollar for dollar above that point. Sport utility vehicles carry a separate cap of $32,000.

These figures come from the OBBBA, which raised the base limits from $1 million and $2.5 million to $2.5 million and $4 million for property placed in service in tax years beginning after December 31, 2024. Both are now indexed for inflation.

Two limits catch owners out. Section 179 cannot create or increase a business loss, because it is capped at your taxable income from the active trade or business. And many states do not conform to the federal limit, so your state return may follow a much lower number.

3. Is bonus depreciation still available in 2026?

Yes, and at 100%. The OBBBA permanently restored the full bonus depreciation deduction under Section 168(k) for qualified property acquired and placed in service after January 19, 2025. Treasury and the IRS issued implementing guidance in Notice 2026-11 in January 2026. Under prior law, bonus depreciation would have fallen to 40% in 2025 and disappeared by 2027.

Points owners regularly miss:

• Used property qualifies, provided the taxpayer had not previously used it and it was acquired in an arm's length transaction.
• Property covered by a written binding contract signed before January 20, 2025 is treated as acquired on the contract date. That can push otherwise eligible assets out of the 100% rule.
• Bonus depreciation has no dollar cap and no phase-out, and unlike Section 179 it can create a net operating loss.
• You can elect out class by class if you would rather spread deductions into later years.

4. Can you deduct R&D costs immediately again?

For domestic research, yes. OBBBA Section 70302 created Section 174A, which restores immediate deduction of domestic research and experimental expenditures for tax years beginning after December 31, 2024. The change is permanent and has no sunset. Foreign research costs remain amortized over 15 years, so the domestic and foreign split has to be documented precisely.

This reaches further than most owners assume. Software development, product engineering, and process improvement work often qualifies, along with the U.S. wages and contractor payments tied to it.

The OBBBA also gave small businesses under the Section 448(c) gross receipts test, roughly $31 million in average annual gross receipts, a route to apply Section 174A retroactively to tax years beginning after December 31, 2021, through amended returns or a change in accounting method under Revenue Procedure 2025-28. That retroactive window has now closed. Verify your position with your CPA before assuming a refund claim is still open.

5. What changed in the QBI deduction for 2026?

The OBBBA made the Section 199A qualified business income deduction permanent, ending the December 31, 2025 sunset. It also added a floor. For tax years beginning after December 31, 2025, a taxpayer with at least $1,000 of qualified business income receives a minimum deduction of $400.

For 2026, Revenue Procedure 2025-32 sets the taxable income thresholds at:

Below the threshold, the 20% deduction applies without the W-2 wage and property tests and without the specified service trade or business restriction. Above the phase-in range, both bite. The planning lever is your taxable income, not your revenue, which is why retirement contributions and depreciation timing interact directly with this deduction.

6. Which home office method actually pays more?

The IRS simplified home office option gives you $5 per square foot of qualifying space, capped at 300 square feet, so $1,500 maximum. It requires no Form 8829, no expense tracking, and no depreciation recapture when you sell.

That simplicity has a price. The regular method deducts the business-use percentage of rent or mortgage interest, utilities, insurance, repairs, and depreciation. For an owner paying $2,800 a month in rent with a 200 square foot office in a 1,400 square foot home, the regular method produces roughly $4,800 in rent alone against $1,000 under the simplified rule.

Two constraints apply either way. The space must be used exclusively and regularly for business, and the deduction cannot exceed the gross income from the business use of the home. Under the simplified method, any excess is lost rather than carried forward.

7. How do S corporation owners deduct home office and vehicle costs?

Through an accountable plan, not a personal deduction. If your S corporation reimburses you for the business use of your home, your personal vehicle, or your cell phone under a written accountable plan, the company deducts the expense and the reimbursement is not taxable wages to you.

An accountable plan has three requirements: a business connection, substantiation of the expense within a reasonable period, and return of any excess advance. Without the written plan, reimbursements are treated as wages, which adds payroll tax on top of the lost deduction.

This is one of the most common omissions in small S corporations. Owners assume that because they cannot claim the home office on Schedule C, the deduction is gone. It is not gone. It moves to the corporate return, and the mechanism is a plan document plus a monthly expense report.

8. How much can you put into a retirement plan in 2026?

Retirement plan contributions remain the largest deduction most profitable owners underuse. Under Notice 2025-67, the 2026 limits are:

• 401(k), 403(b), and governmental 457(b) elective deferral: $24,500, up from $23,500
• Age 50 and over catch-up: $8,000
• SIMPLE IRA deferral: $17,000, or $18,100 for certain plans under SECURE 2.0
• Traditional and Roth IRA: $7,500
• Total annual additions to a defined contribution plan, including SEP IRAs and solo 401(k)s: $72,000, with compensation counted up to $360,000

A solo 401(k) reaches the $72,000 ceiling faster than a SEP IRA at the same income, because it combines an employee deferral with an employer contribution. One catch-up rule now bites: if your FICA wages from an employer in 2025 exceeded $150,000, your 2026 catch-up contributions to that employer's plan must be Roth.

9. Which meal deduction disappeared on January 1, 2026?

This one costs money rather than saving it, and it is the change most likely to produce a surprise on your 2026 return. Under Section 274(o), added by the OBBBA, employers get no deduction for amounts paid after December 31, 2025 for meals furnished for the convenience of the employer under Section 119, or for the costs of an employer operated eating facility. These were generally 50% deductible before.

What still works:

• Business meals with clients or prospects: 50% deductible
• Meals while traveling away from home on business: 50% deductible, unaffected by the change
• Company holiday parties and staff picnics: 100% deductible when structured as recreational events primarily for non-highly-compensated employees
• Food and beverages sold to customers in a bona fide transaction, and meals on certain fishing vessels and at fish processing facilities: full deduction retained

10. Does the new $2,000 Form 1099 threshold change what you can deduct?

No, and that is exactly why it costs owners money. OBBBA Section 70433 raised the Section 6041 information reporting threshold from $600 to $2,000 for payments made after December 31, 2025. Fewer Forms 1099-NEC and 1099-MISC to file.

The deduction rules did not change. A $900 payment to a contractor is still fully deductible as an ordinary and necessary business expense under Section 162. What changes is that no third-party form will exist to remind you it happened. Owners who reconcile deductions against the 1099s they issued will now systematically undercount their contractor spend.

Keep booking every contractor payment regardless of size, and keep collecting Form W-9 before the first payment rather than at year end.

11. Which small employer credits get overlooked?

These are credits and exclusions rather than deductions, and they are worth more per dollar because credits reduce tax directly. For 2026:

• QSEHRA: a qualified small employer health reimbursement arrangement can reimburse up to $6,450 for self-only coverage and $13,100 for family coverage, tax free to the employee
• Section 45R: the small employer health insurance credit uses an average annual wage figure of $34,100 for 2026
• Section 127: employer payments toward an employee's student loans, up to $5,250 a year, are permanently excluded from income
• Section 45S: the paid family and medical leave credit is now permanent, with the employee service requirement lowered from twelve months to six
• Section 45F: the employer-provided childcare credit rises to a maximum of $500,000, or $600,000 for an eligible small business

12. Did you deduct your startup costs?

Under Sections 195 and 248, a new business can deduct up to $5,000 of startup costs and $5,000 of organizational costs in the year it begins operations. Each $5,000 amount phases out dollar for dollar once the respective category exceeds $50,000. Anything remaining is amortized over 180 months.

Startup costs include market research, travel to secure suppliers or customers, professional fees, and staff training incurred before the business opened. Organizational costs cover entity formation: state filing fees, legal drafting of the operating agreement, and initial organizational meetings.

How to choose which deductions to prioritize

You do not need all twelve. Work through these criteria in order.

1. Start with what changed. Items 1, 3, 4, 9, and 10 are 2026 rule changes. A deduction you claimed correctly in 2024 may be wrong this year.
2. Rank by dollars per hour of effort. Retirement contributions and depreciation elections move five figures. Startup cost classification is a one-time exercise. Mileage rate splitting takes ten minutes.
3. Check the loss constraint before electing. If you expect a loss year, Section 179 gives you nothing while bonus depreciation still works.
4. Match the deduction to your entity. The home office deduction and the accountable plan reach the same expense through different returns. Claiming the wrong one produces an error, not a saving.
5. Ask whether the deduction lowers taxable income below a QBI threshold. Pushing 2026 taxable income under $403,500 jointly or $201,750 otherwise can be worth more than the deduction itself.
6. Confirm state conformity. Section 179 and bonus depreciation are the two provisions where states diverge most from federal rules.

Section 179 vs bonus depreciation: side by side

Most owners use both. Section 179 targets specific assets and controls the deduction precisely. Bonus depreciation sweeps up the rest and can push the business into a loss carryforward when that is the better outcome.

Sources and references

• IRS, Revenue Procedure 2025-32, inflation-adjusted figures for tax years beginning in 2026.
• IRS, Notice 2026-10, 2026 standard mileage rates.
• IRS, Announcement 2026-11, mid-year increase in the business standard mileage rate effective July 1, 2026.
• IRS, Notice 2026-11, implementing guidance on 100% bonus depreciation under Section 168(k).
• IRS, Notice 2025-67, 2026 retirement plan contribution limits.
• IRS, Revenue Procedure 2025-28, procedures for Section 174A domestic research expenditures.
• Public Law 119-21, One Big Beautiful Bill Act, enacted July 4, 2025.
• Grant Thornton, Permanent full expensing for U.S. research under the OBBBA.
• Forvis Mazars, IRC Section 274(o) and employer-provided meals from January 1, 2026.

This guide covers U.S. federal rules only and does not address state or local taxes. It is general information, not tax advice for your situation. Confirm any position with a CPA or Enrolled Agent before filing.