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Guides & references
Deep explanations where a single-number fact page doesn't do the job, and single-number reference pages where that's all you need. Every piece is authored by a named analyst, cited to the primary authority (BMF / gesetze-im-internet.de / IRS), and dated. No generic AI explainers — only content an expert would write.
United States · Quarterly estimated tax
- Reference 7 min read
US Quarterly Estimated Tax Deadlines 2026
Every IRS §6654 Q1–Q4 due date for 2026, with safe-harbor math and state quarterly wrinkles.
By Marcus Hale · Last reviewed
Read - Guide 6 min read
Why 1099 quarterly tax catches freelancers off guard
The underpayment-penalty trap, the §6654 safe harbor, and what to set aside starting from your first 1099 gig.
By Marcus Hale · Last reviewed
Read
Accountability. Every number in these pages is traceable to a primary authority and versioned in our public changelog. When something changes, the rule module bumps its dated version and the affected pages update in the same pass. See the full methodology for how we work and where we draw the line against tax advice.