The quality of a tax return is set before anyone touches software — it’s set by what arrives in the folder. Missing documents don’t just slow things down; they become missed deductions, mismatch notices months later, and the dreaded second appointment. Here’s the complete list we give La Crescenta clients — equally useful now if you’re on extension with an October 15 deadline.
The personal stack
- Identity & carryover: last year’s full return (new clients — this is the single most valuable document), plus IDs and dependents’ SSNs.
- Income: W-2s, every 1099 variant (NEC, MISC, INT, DIV, B, K, R, G), K-1s — remember K-1s often arrive late; tell your preparer they’re coming.
- Homeowner items: Form 1098 mortgage interest and your LA County property tax bills (both installments — April and December — not just one).
- California oddities: DMV renewal notices (the license-fee portion can be deductible), CA SDI shown on W-2s, any FTB estimate payments made.
- Life events: a birth, a home sale, stock options exercised, a new rental — flag them even if no form arrived.
The business stack
- The books — a clean P&L and balance sheet beats a bag of receipts by a week of billable time (if the books aren’t clean, that’s the real project).
- Payroll: quarterly 941s/DE 9s, W-3/W-2 copies, any tip reporting records for food service.
- Asset purchases: invoices for equipment, vehicles, improvements — with in-service dates, for depreciation and Section 179 decisions.
- Vehicle & home office: mileage logs (total and business miles) and home-office square footage with household expenses.
- Estimates paid: dates and amounts of every federal and California estimate — misapplied estimates are a top cause of wrong balance-due letters.
The local items owners forget
Your 571-L business property statement copy, the local business license (county or Glendale — territory matters), and CDTFA sales-tax filings for the year. None of these go on the income tax return directly, but each one cross-checks something that does — and inconsistencies between them are exactly what auditors hunt.
One complete folder equals one appointment, every deduction you’re entitled to, and a return that doesn’t generate mail in September. Build the folder all year — a shared drive or a literal manila folder both work — and April becomes administrative instead of archaeological.
Action items
- Start the folder today — whatever month it is
- New to a preparer? Lead with last year’s complete return
- Reconcile the books before the appointment, not during it
- List your estimate payments with dates — don’t make anyone guess
- On extension? The payment was due in April; the paperwork is due October 15 — don’t let the folder wait until October 10
This article is general information, not tax advice for your specific situation. Rules change and details matter — talk to a CPA (we know one) before acting on anything here.