10 Tax Deductions Long Island Business Owners Frequently Miss

Every tax season, we review returns from business owners across Nassau and Suffolk County and find the same thing: legitimate deductions left on the table. Not aggressive loopholes, just ordinary, fully allowable write-offs that were never tracked or never claimed. Over a few years, those misses add up to real money.

Here are ten of the deductions Long Island business owners overlook most often, and what you need to claim each one correctly.

1. The Home Office Deduction

If you use part of your home regularly and exclusively for business, you can deduct a portion of your rent or mortgage interest, utilities, insurance, and repairs. Many owners skip it out of an outdated fear that it triggers an audit. The simplified method (a flat rate per square foot, up to 300 square feet) makes it straightforward, and the regular method based on the actual percentage of your home often deducts more. The key word is exclusively: a desk in the corner of a room you also use personally does not qualify.

2. Business Vehicle and Mileage

If you drive for work, whether to client sites, the bank, or the supply store, those miles are deductible. You can use the standard mileage rate or deduct actual expenses (gas, insurance, repairs, depreciation). The catch is documentation: the IRS expects a contemporaneous log of date, destination, purpose, and miles. Your commute from home to a regular office does not count, but trips between job sites do.

3. Retirement Plan Contributions

A SEP-IRA or Solo 401(k) lets a self-employed owner contribute far more than a standard IRA, and the contributions are deductible. This is one of the largest deductions available to a profitable small business, yet many owners default to a basic IRA and leave tens of thousands of dollars of deductible contribution room unused every year.

4. Self-Employed Health Insurance and HSA

If you are self-employed and not eligible for a spouse's employer plan, you can generally deduct your health, dental, and qualifying long-term care premiums, for yourself and your family, as an adjustment to income. Pair that with a Health Savings Account (if you have a qualifying high-deductible plan) and your HSA contributions are deductible too, while growing tax-free for future medical costs.

5. Section 179 and Equipment Purchases

Rather than depreciating equipment over many years, Section 179 lets you deduct the full cost of qualifying equipment, computers, machinery, off-the-shelf software, and certain vehicles, in the year you place it in service. Bonus depreciation can apply on top of it. For a growing Long Island business buying tools or technology, this can sharply reduce taxable income in a strong year.

6. Business Startup Costs

Launched recently? You can generally deduct up to $5,000 of startup costs and $5,000 of organizational costs in your first year, with the remainder amortized over time. Market research, legal and accounting fees to form the entity, and pre-opening advertising commonly qualify. New owners frequently forget that money spent before the doors opened is deductible at all.

7. Professional Development and Subscriptions

Courses, certifications, license renewals, trade publications, and industry software subscriptions that maintain or improve the skills your business requires are deductible. So are the dues for professional and trade associations. These small recurring charges scatter across the year and are easy to miss when nobody is tracking them by category.

8. Business Meals

Meals with a clear business purpose, a client lunch, a meal while traveling for work, are generally 50% deductible. The standard is that the expense is ordinary, necessary, and not lavish, with a business contact present. Keep the receipt and a quick note of who you met and why. Entertainment (event tickets, a round of golf) is no longer deductible, so keep meals tracked separately.

9. Bank and Merchant Processing Fees

Monthly account fees, wire charges, and the percentage your card processor takes on every sale are all deductible business expenses. For a retailer or service business running most revenue through cards, merchant fees alone can total thousands a year. Because they are deducted automatically and never invoiced, they often never make it into the books.

10. The Qualified Business Income (QBI) Deduction

The QBI deduction can let eligible pass-through owners, sole proprietors, partnerships, and S-corporations, deduct up to 20% of qualified business income. Income thresholds and rules for certain service businesses apply, which is exactly why it gets missed or miscalculated. For many Long Island owners it is one of the most valuable deductions on the return, so it is worth confirming you are claiming the full amount you qualify for.

Quick Recap: The Ten Most-Missed Deductions

• Home office (regular and exclusive use)
• Business vehicle and mileage
• SEP-IRA or Solo 401(k) retirement contributions
• Self-employed health insurance and HSA contributions
• Section 179 equipment and software
• First-year business startup and organizational costs
• Professional development, licenses, and subscriptions
• Business meals (50%)
• Bank and merchant processing fees
• The 20% Qualified Business Income deduction

The common thread is recordkeeping. Most of these are missed not because the owner was ineligible, but because the expense was never tracked to a category or never documented well enough to defend. Clean books are the difference between a deduction you can claim and one you leave behind. If your records need work, see how our accounting and bookkeeping services keep them return-ready year round, and how our tax preparation team makes sure every deduction you earned actually lands on the return.

This article is for informational purposes only and does not constitute tax or legal advice. Deduction eligibility, limits, and thresholds depend on your specific facts and can change with the law. Consult a qualified CPA before claiming a deduction on your return.