Quick overview
Filing a state income tax return successfully requires accuracy, timely payments, and awareness of state-specific rules. Errors—like swapped Social Security numbers, omitted income, incorrect residency claims, or misapplied credits—are common and often avoidable with a short checklist and consistent recordkeeping.
This article explains the most frequent mistakes, practical ways to prevent them, when to amend a return, and where to get authoritative guidance. It also links to related FinHelp guides on amending state returns and determining residency for multistate filers.
Common errors (and how they typically show up)
- Personal identification mistakes: misspelled names, transposed Social Security numbers (SSNs), or wrong filing status. These cause automated rejections or mismatches with state systems (check your SSN against your Social Security card).
- Math and transcription errors: adding or copying numbers incorrectly when filing by hand or when transferring figures between forms and schedules.
- Incomplete income reporting: forgetting freelance/1099 income, rental income, stock sales, or income sourced to a different state.
- Misapplied deductions or credits: assuming federal deductions or credits carry directly to the state level—many do not.
- Residency and allocation mistakes: claiming residency in the wrong state or failing to allocate income properly between states when you work in more than one jurisdiction.
- Bank and direct-deposit errors: incorrect bank routing/account numbers prevent direct-deposit refunds and may trigger paper checks or delays.
- Missing signatures or authorization: paper returns without signatures or e-file returns missing e-signature PINs or authorizations.
Examples from practice: a client submitted a return with a transposed SSN and experienced an immediate rejection; another omitted a freelance 1099, triggering a state notice months later. These are common and avoidable.
Step-by-step prevention checklist
Follow this checklist when preparing your state return to reduce errors:
- Verify identity information
- Confirm the spelling of names exactly as shown on Social Security records.
- Double-check SSNs for you, your spouse, and dependents against original documents.
- Reconcile income sources
- Match all W-2s, 1099s, K-1s, broker statements, and bank interest with the return.
- For freelancers and gig economy income, reconcile bank deposits with reported 1099s and business records.
- Confirm residency and multistate sourcing
- If you lived or worked in more than one state, determine residency and source rules before allocating income. See FinHelp’s guide on [State residency tests and where you owe state taxes](
