What is the most important SE tax action to take every year?

Contributing to a Solo 401k (especially the employer portion, which reduces both SE tax and income tax) consistently is the highest-value annual action for most self-employed workers above $50,000 income. Missing this contributes no tax shelter that year — contribution opportunities are lost.

When is the deadline to establish a Solo 401k?

December 31 of the tax year in which you want contributions to count. You can make contributions after December 31 (up to the tax filing deadline including extensions), but the plan must be established by year-end. If you miss December 31, your earliest option for that tax year is a SEP-IRA (which can be established up to tax filing deadline, including extensions).

What year-end equipment purchases reduce SE tax?

Section 179 allows immediate expensing of qualifying business assets purchased and placed in service during the tax year. Computers, vehicles (business-use portion), software, equipment, and certain building improvements qualify. The purchase must be complete and the asset available for business use by December 31.

How do I confirm my quarterly payments were received by the IRS?

Log into your IRS Online Account at IRS.gov — it shows all payments received and their dates. Alternatively, your bank statement shows the debit date for Electronic Federal Tax Payment System (EFTPS) or Direct Pay transactions. Keep payment confirmation numbers for at least 3 years.

What if I underpaid quarterly taxes in 2025?

If your total annual tax liability minus withholding (if any) exceeds $1,000, you owe the underpayment penalty on each quarter where you underpaid. Calculate this on Form 2210. The safe harbor — paying 100% of prior year’s tax in quarterly installments — prevents the penalty even if you owe more at filing.

Self-Employment Tax Checklist: 10 Things to Do Every Year

Self-employment tax management is a year-round activity, not just a February-to-April scramble. This 10-item annual checklist, done in December each year, ensures you’ve captured every deduction, made accurate quarterly payments, and positioned yourself for the optimal tax outcome.

The Annual SE Tax Checklist

💡When to Run This Checklist

December — before year-end. Many actions (Solo 401k establishment, year-end equipment purchases, income deferral) must be taken by December 31. Running the checklist in February is too late for most optimization opportunities.

Annual SE tax checklist — 10 items with deadlines

Item	Action	Deadline	Stakes If Missed
1. Reconcile business income	Total all revenue; compare to expected	Dec 1	Incorrect quarterly estimates; under/overpayment
2. Maximize business deductions	Review and capture all 2025 expenses	Dec 31	Missed deductions can’t be added after filing (usually)
3. Consider year-end equipment purchase	Section 179 deduction for qualifying assets	Dec 31	Must be purchased and placed in service by Dec 31
4. Maximize Solo 401k contribution	Calculate and contribute employee + employer portions	Dec 31 (establish); April 15 (traditional IRA); Oct 15 (Solo 401k employee)	Lost tax shelter; smaller retirement balance
5. Verify quarterly payments made	Confirm all 4 payments received by IRS	Review now	Underpayment penalties if any missed
6. Calculate Q4 estimated payment	Final quarterly payment due Jan 15	Jan 15	Q4 underpayment penalty if missed
7. Confirm health insurance deduction	Document annual premiums paid	Dec 31 coverage year	Missing significant deduction
8. Review vehicle mileage log	Ensure mileage log is complete and documented	Dec 31	Lost vehicle deduction without documentation
9. Home office measurement	Confirm square footage and exclusive use	Anytime but verify annually	Audit risk without accurate documentation
10. CPA consultation	Annual review and planning session	Q4 ideal	Sub-optimal strategy; missed deductions; surprise at filing

The most time-sensitive items are Solo 401k establishment (must be set up by December 31 of the contribution year, though contributions can be made until tax filing deadline) and year-end equipment purchases (must be placed in service before December 31 to take the Section 179 deduction for that tax year).

Calculate Your Year-End Tax Position

Enter your full-year net SE income and deductions to see your total 2025 liability and whether you need a final Q4 estimated payment.

Open Self-Employment Tax Calculator →

Self-Employment Tax Checklist: 10 Things to Do Every Year

The Annual SE Tax Checklist

Frequently Asked Questions

Frequently Asked Questions

More Self-Employment Tax Guides

How to Use a Self-Employment Tax Calculator: Beginner Guide

Self-Employment Tax Benchmarks: What Should You Expect to Pay?

Self-Employment Tax on $50,000 Net Income: Full Breakdown