Q1 (Jan-Mar) checklist
Make Q4 estimated payment for prior year. File 1099s and W-2s by Jan 31. Review prior-year results once tax return is drafted. Set up retirement contributions (SEP, solo 401k) for prior year if not yet done. Evaluate entity choice for the new year (S-election deadline March 15).
Q2 (Apr-Jun) checklist
Make Q1 estimated payment by April 15. File 1040 (or 4868 extension). Begin tracking current-year income and expenses against budget. Make HSA contributions before April 15. Consider if you need to file Form 2210 with the annualized income method.
Q3 (Jul-Sep) checklist
Make Q2 estimated payment by June 15. Mid-year tax projection — extrapolate first half to estimate full-year tax. Review withholding (if you have W-2 income too). Evaluate large purchases that could qualify for Section 179.
Q4 (Oct-Dec) checklist
Make Q3 estimated payment by Sep 15. Year-end tax projection. Accelerate or defer income and expenses based on bracket strategy. Make charitable contributions. Run QBI deduction analysis. Establish solo 401k by year-end if you want to make elective deferrals. Sell loss positions for tax-loss harvesting (personal investments).
Year-round
Reconcile bank, credit card, and processor statements monthly. File receipts as you go. Update mileage log weekly. Review profit/loss monthly. Adjust estimated payments if income shifts significantly. The taxpayers who never get surprised are the ones who look at the numbers every month.
Where the IRS publishes guidance on this topic
The IRS publishes a layered set of free resources on most small-business tax topics: a relevant publication (usually one of Pub 334, 463, 535, 587, 946, 560, or 583), the instructions to the relevant form, the "Small Business and Self-Employed Tax Center" landing pages on IRS.gov, and the Audit Techniques Guides written for IRS examiners. Reading the agency's own materials is the cheapest tax education available. They are written in plain English, updated annually, and they reflect exactly the framework an examiner will apply if your return is selected.
How experienced filers approach this
Experienced self-employed filers and the CPAs who advise them treat this question as a recurring planning exercise rather than a one-time decision. They model the multi-year tax impact rather than just the current year, document the reasoning in a short workpaper that survives staff turnover and software changes, and revisit the analysis annually as facts and laws change. The discipline is not difficult — a half-day in January with last year's return, the current-year IRS publications, and a spreadsheet — but it is rare among DIY filers, which is precisely why it produces outsized results.