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This reference explains every box on Form W-2, what it means, and how EZFile uses it for tax calculations.

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Identity Fields

What it is: Your Social Security NumberEZFile handling: NEVER stored in full. Only last 4 digits extracted (XXX-XX-NNNN)Form 1040 use: Entered at top of form (full SSN required)Privacy note: This is the most sensitive piece of information on your W-2. EZFile processes it locally and never transmits it.
What it is: Your employer’s federal tax ID numberFormat: XX-XXXXXXXEZFile handling: Stored for reference; not sensitive like SSNForm 1040 use: Not entered directly on Form 1040
What it is: Your employer’s official business informationEZFile handling: Displayed for verificationForm 1040 use: Not entered directlyNote: This should match your employer’s legal name, not necessarily your department or division.
What it is: Employer’s internal tracking number for this W-2EZFile handling: Ignored (not needed for tax filing)Note: Used by employers and payroll companies for recordkeeping
What it is: Your legal name as it appears on your Social Security cardEZFile handling: Used for display and verificationForm 1040 use: Must match exactly on your tax returnImportant: If your name has changed (marriage, divorce, etc.), update it with Social Security Administration before filing.
What it is: Your address as your employer has on fileEZFile handling: Displayed for verificationForm 1040 use: You enter your CURRENT address (may differ from Box f)Note: If you moved during the year, use your current address on Form 1040.

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Core Income & Withholding

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Box 1: Wages, Tips, Other Compensation

Box 1: Your Taxable Federal Wages

What it is: Your total taxable federal wages for the yearThis goes on Form 1040, Line 1aCalculation:
Box 1 = Gross Salary
        - Pre-tax retirement (401k, 403b, 457)
        - Pre-tax HSA contributions
        - Pre-tax health insurance premiums
        - Pre-tax FSA contributions
        - Pre-tax transit benefits
Example:
Gross salary:              $51,333
- 401(k) contributions:    -$4,107
- HSA contributions:       -$1,500
- Health insurance:        -$1,200
= Box 1:                   $44,526
Why it’s lower than your salary: Pre-tax benefits reduce this number. This is a GOOD thing—you’re not taxed on money that went to retirement or health benefits.
Critical: Box 1 is THE number that drives your entire tax return. This is your taxable income for federal purposes.

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Box 2: Federal Income Tax Withheld

Box 2: Your Tax Payments

What it is: Federal income tax your employer already sent to the IRS on your behalfThis goes on Form 1040, Line 25aHow it’s determined: Based on your W-4 form elections:
  • Filing status selection
  • Multiple jobs adjustment
  • Extra withholding amount
  • Allowances (for older W-4s)
EZFile critical use: This is compared to your actual tax liability (Line 24) to determine if you get a refund or owe money.Formula:
If Box 2 > Total Tax (Line 24): You get a REFUND
If Box 2 < Total Tax (Line 24): You OWE money

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Box 3: Social Security Wages

AttributeValue
What it isWages subject to Social Security tax
Rate6.2% (employee share)
2025 Wage Base$176,100 (capped)
Form 1040 useNot entered (verification only)
How it differs from Box 1:
  • Does NOT exclude most pre-tax deductions
  • Retirement contributions (401k, 403b) are still included in Box 3
  • HSA contributions ARE excluded from Box 3
  • Capped at $176,100 for 2025
Validation formula: 
Box 4 should equal Box 3 × 6.2% (within $1 rounding)

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Box 4: Social Security Tax Withheld

Box 4 Validation

What it is: Employee’s share of Social Security tax (6.2% of Box 3)Expected value:
Box 4 = Box 3 × 0.062
2025 Maximum: 10,918.20(10,918.20 (176,100 × 6.2%)Validation check:
actual_rate = Box 4 / Box 3

If |actual_rate - 0.062| > 0.001:
    Flag for review
Example:
Box 3: $50,000
Expected Box 4: $50,000 × 0.062 = $3,100
Actual Box 4: $3,100 ✓

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Box 5: Medicare Wages and Tips

AttributeValue
What it isWages subject to Medicare tax
Rate1.45% (employee share)
Wage BaseNo limit (all wages taxed)
Additional Medicare0.9% on wages over $200,000
Form 1040 useNot entered (verification only)
How it differs from Box 3:
  • No wage cap (all wages subject to Medicare)
  • Usually equals Box 3 unless wages exceed Social Security cap ($176,100)
Validation formula: 
Box 6 should equal Box 5 × 1.45% (within $1 rounding)

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Box 6: Medicare Tax Withheld

Box 6 Validation

What it is: Employee’s share of Medicare tax (1.45% of Box 5)Expected value:
Box 6 = Box 5 × 0.0145
Additional Medicare Tax: If Box 5 > $200,000:
Box 6 = Box 5 × 0.0145 + (Box 5 - $200,000) × 0.009
Validation check:
If Box 5 <= $200,000:
    expected_rate = 0.0145
Else:
    expected_rate = (Box 6 / Box 5)

If |actual_rate - expected_rate| > 0.001:
    Flag for review
Example:
Box 5: $50,000
Expected Box 6: $50,000 × 0.0145 = $725
Actual Box 6: $725 ✓

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Special Situations (Boxes 7-11)

What it is: Tips you reported to your employer that are subject to Social Security taxEZFile relevance: Used for Schedule 1-A tip deduction calculationNote: Tips are already included in Box 1 (wages). Do NOT add Box 7 to Box 1.Common for: Restaurant servers, bartenders, delivery drivers, hairstylistsSchedule 1-A deduction: Tips may qualify for a deduction (new for 2025)
What it is: Tips allocated by employer for large food/beverage establishmentsImportant: Allocated tips are NOT included in Box 1—you may need to add them as incomeEZFile handling: Rare for the target user; flag if presentNote: Only applies to large restaurants (8+ employees during a typical business day)
What it is: Historically used for advance EIC payments; now often blank or used for verificationEZFile handling: Ignored
What it is: Employer-provided dependent care assistance (Dependent Care FSA)EZFile relevance: N/A (no dependents in scope)Note: If present for single filers with no dependents, it’s informational only
What it is: Distributions from nonqualified deferred compensation plansEZFile handling: Already included in Box 1; informational onlyNote: Rare for typical W-2 employees

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Box 12: Coded Entries (Critical)

Format: Each entry has a letter code and dollar amount (up to 4 entries: 12a, 12b, 12c, 12d)

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Common Box 12 Codes

CodeDescriptionAlready Excluded from Box 1?EZFile Impact
D401(k) elective deferralsYESUsed for Saver’s Credit eligibility
E403(b) contributionsYESUsed for Saver’s Credit eligibility
G457(b) contributionsYESUsed for Saver’s Credit eligibility
WHSA employer contributionsYESInformational only
AARoth 401(k) contributionsNO (after-tax)Used for Saver’s Credit eligibility
BBRoth 403(b) contributionsNO (after-tax)Used for Saver’s Credit eligibility
DDHealth insurance costN/AInformational only (NOT deductible)
CGroup-term life insurance >$50KNO (taxable)Already included in Box 1
CRITICAL: Codes D, E, G, and W are ALREADY excluded from Box 1. Do NOT subtract them again. They appear in Box 12 for information and Saver’s Credit calculations only.

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Saver’s Credit Relevance

Codes D, E, G, AA, BB represent retirement contributions eligible for the Saver’s Credit (Form 8880). Eligibility:
  • AGI ≤ $39,500 (single filer)
  • Made retirement contributions during the year
  • Ages 18+, not a full-time student, not claimed as dependent
Credit calculation: 
Eligible contributions = sum of Box 12 codes D, E, G, AA, BB
Max eligible: $2,000

Credit rate based on AGI:
- 50% if AGI ≤ $23,750
- 20% if AGI $23,751 - $25,850
- 10% if AGI $25,851 - $39,500

Credit = min(contributions, $2,000) × credit_rate

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Box 13: Checkboxes

What it means: You’re an employee treated as self-employed for certain purposesEZFile handling: Out of scope—refer to tax professionalCommon for: Agent-drivers, commission-drivers, traveling salespeople, certain home workersNote: If checked, you file Schedule C, not just Form 1040

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Box 14: Other

What it is: Employer-specific codes for additional information Common Box 14 entries:
EntryDescriptionTax Impact
SDI / CASDIState disability insuranceState-specific; not federally deductible
Union duesLabor union membership duesMay be deductible (itemized)
UniformUniform allowance or costInformational
Ed AsstEducational assistanceExcluded from income (up to $5,250)
LSTLocal Service Tax (PA)Already withheld; informational
VPDIVoluntary plan disability insuranceState-specific
EZFile handling: Box 14 is usually informational. Some states use Box 14 data for state returns. EZFile displays to user but does not use in federal calculations unless specifically recognized.

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State & Local Fields (Boxes 15-20)

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Box 15: State / Employer’s State ID

FieldDescription
StateTwo-letter state code (e.g., PA, NY, CA)
Employer’s state IDEmployer’s state tax identification number
EZFile useDetermines which state return is needed

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Box 16: State Wages, Tips, Etc.

State Wages (Box 16)

What it is: Wages subject to state income taxMay differ from Box 1 because:
  • States have different pre-tax deduction rules
  • Some states tax certain benefits that are federally excluded
  • Some states exclude certain income that’s federally taxable
EZFile use: Base for state tax calculationExample (Pennsylvania):
Federal wages (Box 1):    $44,526  (excludes 401k)
State wages (Box 16):     $48,633  (includes 401k)
Difference:               $4,107   (PA taxes retirement contributions)

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Box 17: State Income Tax

What it is: State income tax withheld by employer EZFile use: Compared to state tax liability to determine state refund or amount owed Formula: 
If Box 17 > State Tax Calculated: State REFUND
If Box 17 < State Tax Calculated: State OWED

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Boxes 18-20: Local Taxes

BoxFieldDescription
18Local wagesWages subject to local income tax
19Local income taxLocal tax withheld
20Locality nameName or code of local jurisdiction
Common in these states:
  • Pennsylvania (local EIT tax)
  • Ohio (city/school district taxes)
  • New York (NYC, Yonkers)
  • Indiana (county taxes)
  • Maryland (county taxes)
EZFile use: Calculates local tax refund/owed (if applicable)

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Validation Rules

After extracting W-2 data, verify these relationships: 
# Social Security tax check
assert abs(box_4 - (box_3 * 0.062)) <= 1.00, "Box 4 validation failed"

# Medicare tax check
if box_5 <= 200000:
    expected_medicare = box_5 * 0.0145
else:
    expected_medicare = box_5 * 0.0145 + (box_5 - 200000) * 0.009

assert abs(box_6 - expected_medicare) <= 1.00, "Box 6 validation failed"

# Wage base check
assert box_3 <= 176100, "Box 3 exceeds 2025 SS wage base"

# Relationship check
assert box_5 >= box_3, "Box 5 (Medicare) should be >= Box 3 (SS)"
If any validation check fails by more than $1, flag the W-2 for user review. There may be data extraction errors or unusual payroll situations.

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Quick Reference: Box-to-Form Mapping

W-2 BoxForm 1040 LineDescription
Box 1Line 1aWages, salaries, tips
Box 2Line 25aFederal income tax withheld
Box 3(Validation only)Social Security wages
Box 4(Validation only)Social Security tax withheld
Box 5(Validation only)Medicare wages
Box 6(Validation only)Medicare tax withheld
Box 7Schedule 1-A, Line 1Social Security tips (tip deduction)
Box 12 (D,E,G,AA,BB)Form 8880Retirement contributions (Saver’s Credit)
Box 16State returnState wages
Box 17State returnState tax withheld
Only Box 1 and Box 2 directly transfer to Form 1040. Other boxes are used for validation, credits, or state returns.

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