Quarterly Tax Onboarding Checklist

Complete checklist of information needed to accurately calculate your quarterly estimated tax payments. Gather these documents and details before using our calculator or consulting with a tax professional.

Why This Checklist Matters

Having all this information ready ensures accurate quarterly tax calculations, helps you avoid underpayment penalties, and allows you to take advantage of safe harbor rules. Missing information can lead to incorrect estimates and potential penalties.

Identity & Filing Basics

  • Full legal name
  • SSN/ITIN (US) or national tax number
  • Filing status (Single, Married, Head of Household)
  • Business name (if applicable)
  • Entity type (Sole proprietor, Partnership, LLC, S-Corp, C-Corp)
  • Fiscal year (Calendar vs Fiscal)
  • State of residence and nexus states

Prior Year Tax Return

Needed for safe harbor calculations (100% or 110% of prior year rule)

  • Last year's total tax liability (Form 1040, line 24)
  • Adjusted Gross Income (AGI) from prior year
  • Refunds or overpayments from prior year
  • Tax paid via withholding (W-2 withholding)
  • Copy of complete prior year return (Form 1040 + all schedules)

Current Year Income Estimates

  • W-2 wages (with employer withholding amounts)
  • 1099/contractor income (gross and timing by quarter)
  • Business net profit (projected monthly or quarterly)
  • Investment income: dividends, interest, capital gains (amounts and expected dates)
  • Rental income, royalties, pensions, retirement distributions
  • Unemployment income
  • Lump-sum events (stock sale, inheritance) - expected quarter/timing

Expected Adjustments, Deductions & Credits

  • Itemized deductions vs standard deduction choice
  • Above-the-line adjustments (retirement contributions, HSA, SEP IRA)
  • Business expense estimates (COGS, rent, utilities, contractor labor)
  • Home office deduction
  • Vehicle/mileage deductions
  • Tax credits (child tax credit, earned income credit, etc.)

Payroll & Employment Details (if applicable)

Only needed if you have employees or are an S-Corp owner

  • Payroll schedule and frequency
  • Owner salary (S-Corp reasonable compensation)
  • Employer payroll taxes withheld
  • FUTA/SUTA obligations
  • Expected payroll tax deposits

Withholding & Payments Already Made

  • Year-to-date federal & state withholding
  • Estimated tax payments already made this year (dates and amounts)
  • Any AMT or other prior liabilities
  • Payment confirmation numbers

Banking & Payment Details

  • Bank routing number and account number (for EFTPS/Direct Pay)
  • Authorization to schedule payments on your behalf (if using tax preparer)
  • EIN for businesses
  • Preferred payment method (EFTPS, Direct Pay, mail)

Special Circumstances

  • Farmers/fishermen exceptions
  • Casualty/disaster relief
  • Expatriates or nonresident aliens (different rules/forms)
  • Recent large income changes
  • State residency changes
  • Multiple state tax obligations

Ready to Calculate?

Once you have gathered the necessary information, use our free quarterly tax calculator to estimate your payments.

Important Reminders

  • •Keep Records: Maintain copies of all documents and payment confirmations for at least 3 years.
  • •Update Regularly: Recalculate quarterly payments as your income changes throughout the year.
  • •State Requirements: Many states have separate quarterly tax requirements. Check your state's tax agency website.
  • •Professional Help: For complex situations (multiple income sources, S-Corp, partnerships), consider consulting a tax professional.