Every tax season, we review prior-year returns for new clients and find the same handful of deductions missing, again and again. Most weren’t intentionally skipped — they were simply never asked about.
The Home Office Deduction, Even for Part-Time Use
Many owners assume they need a fully dedicated room to claim a home office deduction, or that it’s not worth the “audit risk.” In reality, the space just needs to be used regularly and exclusively for business, and the deduction is calculated using a straightforward simplified method if you’d rather avoid detailed expense tracking.
Vehicle Mileage for Business Use of a Personal Car
If you use a personal vehicle for client visits, supply runs, or business errands, that mileage is deductible even if the car is also used personally. The most common miss isn’t forgetting the deduction exists — it’s not keeping a mileage log detailed enough to substantiate it.
Startup and Organizational Costs
Costs incurred before your business officially opened — market research, legal fees, initial marketing — are often deductible up to a certain limit in your first year, with the remainder amortized over time. Many first-year filers don’t realize pre-launch expenses count at all.
Retirement Plan Contributions
SEP IRA, Solo 401(k), and similar contributions reduce taxable income significantly, but the deadline to open certain plans falls before year-end even though funding deadlines can extend later. Owners frequently miss the window simply because nobody flagged it in time.
Professional Development and Education
Courses, certifications, and conferences directly related to maintaining or improving skills in your current business are deductible, but personal enrichment or training for a new, unrelated field generally isn’t. The distinction trips up more filers than you’d expect.
Bad Debt Write-Offs
If a client never pays an invoice you’d already recognized as income (on an accrual basis), that unpaid amount may be deductible as bad debt. It’s frequently missed simply because nobody revisits old, uncollected invoices at tax time.
The Bottom Line
Most missed deductions aren’t complicated — they’re just easy to overlook without someone specifically asking about them. A second look at a prior-year return, even a well-prepared one, often turns up savings that were sitting there the whole time.
