The Milestone Resource Library
Calendars, playbooks, calculators, and curated reference for the decisions you need to make this quarter — and the ones you should be preparing for two quarters out.
2026 Tax Deadline Calendar
A complete year of IRS and California filing deadlines, organized by entity type. Each entry includes the form number, who it applies to, and what happens if missed. Download the full PDF or browse the interactive table below.
Browse on Screen
Tap a category chip to focus on the deadlines that apply to you.
| Date | Category | What's Due | Form |
|---|---|---|---|
| JAN 15 | Individuals | Q4 2025 Estimated Tax Payment | 1040-ES |
| JAN 31 | Payroll | W-2 to Employees, 1099-NEC Filings | W-2 / 1099-NEC |
| JAN 31 | Payroll | Form 940 — Federal Unemployment | 940 |
| MAR 16 | S-Corp / Partnership | S-Corp & Partnership Returns (or Extension) | 1120-S / 1065 |
| MAR 16 | California | California S-Corp & Partnership Returns | 100S / 565 / 568 |
| APR 15 | Individuals | Individual Tax Return (or Extension) | 1040 |
| APR 15 | Individuals | Q1 2026 Estimated Tax | 1040-ES |
| APR 15 | Individuals | FBAR — Foreign Bank Account Report | FinCEN 114 |
| APR 15 | Individuals | Gift Tax Return (or Extension) | 709 |
| APR 15 | Individuals | Final IRA & HSA Contribution | IRA / HSA |
| APR 15 | C-Corp | C-Corp Return (or Extension) | 1120 |
| APR 15 | Trusts & Estates | Trust & Estate Income Tax Return | 1041 |
| APR 15 | California | California LLC $800 Annual Tax | 3522 |
| APR 30 | Payroll | Form 941 — Q1 2026 | 941 |
| MAY 15 | Nonprofits | Form 990 — Nonprofit Annual Return | 990 |
| JUN 15 | Individuals | Q2 2026 Estimated Tax | 1040-ES |
| JUN 15 | California | California PTET Q1 Prepayment | 3893 |
| JUL 31 | Payroll | Form 941 — Q2 2026 | 941 |
| JUL 31 | S-Corp / Partnership | Form 5500 — Retirement Plan Filing | 5500 |
| SEP 15 | S-Corp / Partnership | Extended S-Corp & Partnership Returns | 1120-S / 1065 |
| SEP 15 | Individuals | Q3 2026 Estimated Tax | 1040-ES |
| SEP 15 | C-Corp | Extended C-Corp Return | 1120 |
| SEP 30 | Trusts & Estates | Extended Trust & Estate Return | 1041 |
| OCT 15 | Individuals | Extended Individual Return | 1040 |
| OCT 15 | Individuals | SEP-IRA / Solo 401(k) Final Contribution | Retirement |
| OCT 31 | Payroll | Form 941 — Q3 2026 | 941 |
| NOV 15 | Nonprofits | Extended Form 990 | 990 |
| DEC 15 | C-Corp | Q4 C-Corp Estimated Tax | 1120-W |
| DEC 31 | Individuals | RMD Deadline (age 73+) | RMD |
| DEC 31 | Individuals | Year-End Tax Planning Deadlines | Various |
The Milestone Playbooks
Each playbook covers a specific high-stakes area — written for owners, investors, and families who want decision-grade content, not generic tips. Free to download.
PLAYBOOK 01 · HNW
The annual window between October and December where most six-figure tax decisions happen. PTET elections, Roth conversions, charitable bunching, RMD coordination, and the structural moves that compound across years.
Best for: For HNW families with $2M+ in liquid wealth, business income, or significant capital gains.
PLAYBOOK 02 · REAL ESTATE
Cost segregation studies, real estate professional status (REPS), 1031 exchanges, opportunity zones, and the holding structures that hold them. The aggressive tax positions that turn rental income into tax-advantaged returns.
Best for: For investors with active portfolios — single-family rentals, commercial, or short-term.
PLAYBOOK 03 · OWNERS
25 questions across Financial Readiness, Structural Cleanup, Valuation Drivers, and Owner Succession. Score yourself honestly and see where the gap is between the business you have and the business that's sellable for full value.
Best for: For owners 3-7 years from a planned exit or transition.
PLAYBOOK 04 · MULTI-STATE
Remote employees, SaaS customers, marketplace facilitators, out-of-state contractors. Where you owe in 2026 — and what voluntary disclosure looks like if you find exposure. State-by-state thresholds and a clean-up framework.
Best for: For SaaS founders, professional services firms, and any business with remote workforce.
PLAYBOOK 05 · FAMILY OFFICE
DAFs, QCDs, CRTs, private foundations, and appreciated-asset gifts. How each vehicle works, when each fits, and how they layer together. Written for families giving $25K+ annually who want the tax benefit to match the charitable intent.
Best for: For families with $5M+ net worth and substantive charitable giving.
Calculators & Tools
Self-service tools that give a directional answer. For an actual return-on-effort number, schedule a 30-minute review.
How much an S-corp election would save your business based on net income, reasonable comp, and California payroll considerations.
Read the guide →Estimate the Year 1 depreciation unlock for your commercial or residential rental property, including bonus depreciation considerations.
Read the guide →Project your federal and California estimated payments based on YTD income, prior year safe harbor, and expected Q4 income.
Read the guide →The Wayfair threshold checklist and a state-by-state decision tree for sales tax, income tax, and payroll obligations.
Download playbook →25-question self-assessment across financial, structural, valuation, and succession readiness. Find the gap before a buyer does.
Download scorecard →Our 10-item playbook of what we run for HNW clients in November and December — including the dates each move needs to happen.
Download playbook →Official Resources Library
Authoritative government, regulatory, and industry-association resources organized by topic. Verify a license, file with an agency, look up a rate, or learn from a free guide. All open in new tabs.
Federal · IRS
California · FTB
California · EDD
Entity & Compliance
Investments · SEC + FINRA
Markets · Economic Data
Loans, Banks & Mortgages
Insurance & Consumer Protection
Retirement · SSA · Medicare
Estate Planning · Trusts
Real Estate · Licensing
Real Estate · Property & Tax
Healthcare · Medical & Dental
Therapy & Mental Health
Labor · HR · IP
Education + Bay Area
From the Milestone Journal
Practical commentary on tax planning, structure, and the questions our clients keep asking.
An Invitation
A complimentary 30-minute review. We look at your situation specifically — entity, income, family, state — and tell you what we’d actually do. If we’re a fit, you’ll know. If we’re not, we’ll say so.
Call directly: 925-320-0309 · ronak@milestonecpas.com
