A box is a starting point.
Read a W-2 or partnership K-1 by following the category, not just the dollar amount. Explore 23 fields with fictional examples, reporting paths, and the questions still left to answer.
The map below is not a filing form and does not reproduce every box. The explanations use archived 2025 IRS forms and instructions. No real documents or financial data are requested. All amounts are fictional.
W-2
Fictional employee: $80,000 gross wages, $5,000 traditional 401(k) deferral, no tips or other payroll adjustments. California is the only state line.
Wages, payroll taxes, and withholding
Selected fields only. Not an IRS form. Do not file.Choose a field to follow its meaning and reporting path.
Box / item 1 Federal wages
What it means
The employer reports compensation included in federal taxable wages. This is a wage-income starting point, before the deductions and credits applied on the individual return.
What it does not settle
Box 1 is neither take-home pay nor AGI. Pretax benefits can make it differ from Social Security and Medicare wages. Do not deduct the same payroll deferral a second time.
Our fictional employee earns $80,000 and defers $5,000 into a traditional 401(k). With no other adjustments, box 1 is $75,000.
Box / item 2 Federal income tax withheld
What it means
This is federal income tax the employer withheld and remitted during the year. On the return, it belongs on the payment side of the calculation.
What it does not settle
Withholding is a prepayment, not the final income-tax liability. A refund can change because payments changed even when the underlying tax did not.
Suppose the completed return has $8,000 of total tax and only $9,000 of withholding. The simplified difference is a $1,000 refund. It is not a $1,000 reduction of tax.
Box / item 3 Social Security wages
What it means
This is the wage base the employer reports for Social Security tax, subject to the annual wage-base limit and separate tip reporting. It can include traditional 401(k) deferrals excluded from box 1.
What it does not settle
Do not add boxes 1, 3, and 5 as three sources of income. They describe overlapping wage bases under different tax systems.
In this example, box 3 is $80,000 while box 1 is $75,000. The $5,000 difference is the traditional 401(k) deferral, not unreported extra pay.
Box / item 4 Social Security tax withheld
What it means
This box reports the employee Social Security tax withheld. The fictional $80,000 wage base is below the 2025 annual limit, so the ordinary 6.2% employee rate produces $4,960.
What it does not settle
This is separate from federal income-tax withholding in box 2. Excess tax caused by multiple employers and an error by one employer follow different correction routes.
$80,000 × 6.2% = $4,960. The arithmetic is a consistency check for this simple example, not a determination of every special payroll situation.
Box / item 5 Medicare wages and tips
What it means
Medicare uses its own wage base. Traditional elective deferrals can remain in this base even when excluded from federal wages. Unlike Social Security, regular Medicare tax has no annual wage cap.
What it does not settle
A difference from box 1 can be correct. Additional Medicare Tax uses further rules, and its final return calculation can differ from what an employer withheld.
For our fictional employee, the $5,000 traditional 401(k) deferral remains in the $80,000 Medicare wage base.
Box / item 6 Medicare tax withheld
What it means
The box reports employee Medicare withholding, including Additional Medicare withholding when applicable. The basic employee rate in the simple example is 1.45%.
What it does not settle
Do not treat this as an income-tax payment from box 2. Additional Medicare is reconciled under its own return rules; withholding alone does not establish the final amount.
$80,000 × 1.45% = $1,160. This example has no Additional Medicare withholding.
Box / item 12 Coded information
What it means
The letter is part of the information. Code D identifies elective deferrals to a section 401(k) arrangement; other letters identify different benefits or tax items. The printed slots 12a–12d are not the codes themselves.
What it does not settle
A box 12 amount is not automatically additional taxable income or an additional deduction. Read the actual letter and the year-specific instructions.
D $5,000 explains our wage difference. Code DD, by contrast, describes the reported cost of employer-sponsored health coverage and does not itself make that amount taxable.
Box / item 13 Retirement-plan checkbox
What it means
The retirement-plan indicator reports coverage under the applicable employer-plan rules. It can matter when examining a deduction for a traditional IRA contribution.
What it does not settle
It does not state the account balance, the contribution limit, or that an IRA contribution is entirely deductible or prohibited. Income and filing-status rules require separate analysis.
In our example, the employee made a traditional 401(k) deferral and the retirement-plan checkbox is marked. An IRA question still needs its own facts.
Box / item 16 State wages
What it means
State wages are reported beside the state identification in box 15. The state wage base can differ from federal wages because state law and sourcing rules can differ.
What it does not settle
This box alone does not determine residency, where services were performed, or how a multistate return allocates wages. Multiple state lines may refer to overlapping compensation.
Our illustration uses a single California state line of $75,000. It deliberately contains no interstate work or residency change.
Box / item 17 State income tax withheld
What it means
This is state income tax withheld for the state identified on that W-2 line. It is a payment toward that state’s tax, separate from the federal payment in box 2.
What it does not settle
It does not establish the final state tax, and it should not be added to federal withholding as though both were paid to the IRS. Any federal itemized-deduction treatment is a separate question.
The fictional $3,000 is California withholding. Compare it with the completed California return, not with federal tax alone.
Schedule K-1 (Form 1065)
Fictional selected partnership fields. Ordinary income is after partnership-level deductions. The numbers illustrate different categories; they do not prepare a partner’s return.
Allocations, payments, capital, and debt
Selected fields only. Not an IRS form. Do not file.Choose a field to follow its meaning and reporting path.
Box / item 1 Ordinary business income / loss
What it means
This is the partner’s reported share of ordinary business results. A partnership can allocate taxable income even when it retains the cash. The partner applies the relevant reporting and limitation rules.
What it does not settle
The amount does not answer whether a loss is currently deductible, whether an activity is passive, or the self-employment-tax result. Box 14 and activity statements can matter.
The $12,000 allocation and the $8,000 cash distribution in box 19 are different events. Do not replace income with the cash received.
Box / item 2 Net rental real-estate income / loss
What it means
The rental real-estate result is separately identified so partner-level activity rules can be examined. A partnership may attach statements identifying multiple properties or activities.
What it does not settle
A rental loss is not automatically deductible against wages. Basis, at-risk, passive-activity, and other applicable limits are distinct inquiries.
Our $2,000 is a positive rental allocation. Replacing it with a loss would require additional analysis, rather than simply subtracting it from wages.
Box / item 4a Guaranteed payments for services
What it means
This line identifies guaranteed payments for services. The concept under §707(c) depends on how the amount is determined, rather than merely calling a bank transfer an owner draw.
What it does not settle
This is not W-2 employee pay, and it should not be added again to the total in box 4c. Deductibility to the partnership and self-employment-tax treatment require their own rules.
Our service component is $5,000. Together with $1,000 for capital, it produces the $6,000 total in box 4c.
Box / item 4b Guaranteed payments for capital
What it means
This component identifies guaranteed payments for the use of capital, distinguished on the K-1 from payments for services. The agreement and actual arrangement remain relevant.
What it does not settle
A preferred distribution is not automatically a guaranteed payment. Do not infer characterization from the cash amount or the word “guaranteed” alone.
The fictional $1,000 capital payment is included in the $6,000 box 4c total; it is not a second $1,000 on top of that total.
Box / item 4c Total guaranteed payments
What it means
The total combines the service and capital components. It helps reconcile the K-1, while the separate components preserve information about the nature of the payment.
What it does not settle
Do not sum boxes 4a + 4b + 4c as three independent income amounts. That would count the same guaranteed payments twice.
$5,000 + $1,000 = $6,000. Adding all three printed amounts would incorrectly produce $12,000.
Box / item 5 Interest income
What it means
Interest retains a separate reporting identity rather than disappearing into ordinary business income. The partner applies the rules relevant to that type of income.
What it does not settle
Do not add it to box 1 and then report it again separately. Tax-exempt interest is a different category and is not identified by this ordinary interest box.
The fictional $300 remains separately stated even though it came through the same partnership as the $12,000 business allocation.
Box / item 8 Net short-term capital gain / loss
What it means
This capital item retains its short-term character. It joins the partner’s other relevant capital transactions through the capital-gain and loss reporting process.
What it does not settle
A $250 short-term loss is not automatically a $250 current deduction against wages. Capital netting, loss limits, and other applicable rules come first.
Our −$250 is one input to the capital schedule, alongside the $2,000 long-term gain and any other capital items held personally.
Box / item 9a Net long-term capital gain / loss
What it means
A long-term capital item passes through with its character. The partner combines it with other capital items and applies the relevant individual rate and limitation rules.
What it does not settle
Box 9a alone does not establish a flat 15% tax. Income stacking, filing status, capital netting, and separately reported special gains can change the result.
The $2,000 is a gain amount, not the tax due. Multiplying it by 15% without the rest of the return would skip necessary facts.
Box / item 13 Other deductions: read the code
What it means
Box 13 uses letter codes and attached statements to identify deductions. Different codes can lead to different forms, limits, or information requirements.
What it does not settle
The entire box is not a universal deduction from box 1. An allocation on the K-1 does not establish that the partner can currently claim the full amount.
Our code A $500 identifies cash charitable contributions in the 60%-of-AGI category under the 2025 instructions. The partner still applies the itemizing, substantiation, and limitation rules.
Box / item 19 Distributions: cash is a separate event
What it means
This box identifies distributions by code. A simple money distribution generally reduces outside basis; money exceeding the applicable basis can trigger gain. Property and certain securities require additional rules.
What it does not settle
A distribution is not automatically the partner’s taxable income or automatically tax-free. Liability reductions can be treated as money, and special distribution rules can apply.
The $8,000 cash distribution is not a substitute for the $12,000 income allocation. Our ledger example treats both events separately.
Box / item 20 Other information: keep the attachments
What it means
Box 20 is a coded information channel. For example, code Z directs attention to section 199A information, commonly supplied in a statement rather than one self-sufficient deduction amount.
What it does not settle
A code is not a conclusion. A positive business allocation does not by itself establish a QBI deduction; eligibility, component definitions, and limitations need separate analysis.
The fictional K-1 says “Z — statement.” A useful next step is reading that statement, not treating the letter as an extra dollar amount.
Box / item L Tax-basis capital account
What it means
Item L reports the capital-account analysis using the tax-basis method for 2025. It is an important reconciliation but is different from both §704(b) book capital and the partner’s outside basis.
What it does not settle
A partner’s share of partnership liabilities is not included in tax-basis capital. Other partner-specific differences may also exist; a negative capital balance is not automatically negative outside basis.
Simplified capital: $20,000 opening + $15,550 net capital increases − $8,000 distributions = $27,550. Guaranteed payments are not added again as the partner’s capital income.
Box / item K1 Partner’s share of liabilities
What it means
The form separates nonrecourse, qualified nonrecourse financing, and recourse liabilities. Changes in liability shares can affect outside basis and can be treated as money contributed or distributed under §752.
What it does not settle
The debt amount does not automatically equal the amount at risk. Debt allocation depends on its own rules, and the three categories should not be collapsed without analysis.
Only if there are no other differences, ending capital $27,550 plus a $14,000 liability share would give $41,550 outside basis. This is an illustration, not a general reconstruction formula.
Three distinctions to remember.
- Withholding is a payment. The tax return determines liability; payments help determine the refund or balance.
- Allocated income is not cash. A K-1 allocation and a distribution must be analyzed separately.
- Capital is not outside basis. Keep a separate partner-level basis schedule and analyze liabilities under their own rules.
Reviewed November 15, 2026. Guide edition: 2025 forms. The sources and actual facts control; reporting paths are conceptual, not complete filing instructions.