Box d is in the left-hand column of your W-2, directly below Box c (your employer’s name and address) and directly above Box e (your name). It holds an optional control number your employer’s payroll system uses for internal record-keeping. The IRS does not need it to process your return, and if the box is blank on your W-2, the form is still valid.
Locating Box d on the Form
A standard W-2 has two sides. The left column carries lettered boxes (a through f) with identifying information about you and your employer. The right side carries numbered boxes (1 through 20) with your wages, taxes withheld, and other compensation figures. Box d sits in that left column between Box c above it and Box e below it.1Internal Revenue Service. General Instructions for Forms W-2 and W-3 (2026)
Payroll software vendors design their own print layouts, so spacing on your W-2 may not match another employer’s form exactly. Some versions compress the left column or shift boxes to fit the page. The letter “d” printed next to the box does not change, so scanning the left column for that label is the fastest way to find it.
What the Control Number Is
The entry in Box d is an alphanumeric code your employer’s payroll system assigns to identify your specific W-2 within its own records. It works like an internal filing reference that helps payroll staff pull up or sort individual forms.2Internal Revenue Service. 2026 General Instructions for Forms W-2 and W-3 – Specific Instructions for Form W-2
The IRS and the Social Security Administration do not assign this number and do not use it. It plays no part in calculating your tax, verifying your income, or determining credits or deductions. The SSA’s electronic filing format does not even include a field for it.3Social Security Administration. Specifications for Filing Forms W-2 Electronically (EFW2)
That is different from the number in Box b. Box b holds your employer’s Employer Identification Number, a federally assigned nine-digit number formatted as XX-XXXXXXX, which the IRS does use to match your reported wages with your employer’s filings.2Internal Revenue Service. 2026 General Instructions for Forms W-2 and W-3 – Specific Instructions for Form W-2 The control number in Box d has no standard format.
IRS specifications allow the control number to run up to 14 characters and to include letters, numbers, and a handful of special characters: hyphens, slashes, commas, ampersands, and plus signs.4Internal Revenue Service. Form W-2 Wage and Tax Statement Field Identification Some employers use a short numeric code, others a longer mix of letters and numbers. There is no correct format.
If Box d Is Blank
The IRS instructions state that employers do not have to use Box d.2Internal Revenue Service. 2026 General Instructions for Forms W-2 and W-3 – Specific Instructions for Form W-2 A blank Box d means your employer’s payroll system did not assign a control number to your form. It is not a sign of missing income data, a processing error, or a problem with the W-2.
You do not need to contact your employer or request a corrected Form W-2c over a blank Box d. Everything the IRS and SSA actually rely on is elsewhere on the form: your wages in Box 1, federal tax withheld in Box 2, Social Security and Medicare figures in Boxes 3 through 6, and your Social Security number in Box a.
Entering Box d in Tax Software
Most consumer tax software gives you a field for the Box d control number when you enter your W-2. If your form has a control number, type it exactly as printed, including any hyphens, slashes, or spaces. Matching the digital entry to the physical document can help later if you need to amend the return.
If Box d is blank, leave the field empty and keep going. The software will not reject your return over a missing control number. Some programs occasionally display a warning or formatting error when the field is empty; entering a placeholder such as a string of zeros usually clears it. The IRS does not use the control number to validate your return, so a placeholder causes no filing problem.
Some tax programs also let you import W-2 data directly from your IRS online account instead of typing it in.5Internal Revenue Service. Import Your Tax Information Into Tax Preparation Software When you use that feature, the software pulls the wage and tax data the IRS already has on file. The control number may or may not carry over, but either way it will not change the accuracy of your return.
The Lettered Boxes Around Box d
It helps to know what Box d’s neighbors contain when you are scanning the form:
- Box a: your Social Security number.
- Box b: your employer’s Employer Identification Number (EIN).
- Box c: your employer’s name, address, and ZIP code.
- Box d: the optional control number.
- Box e: your first and last name.
- Box f: your address.
The numbered boxes to the right, 1 through 20, hold your actual wage and tax figures, which are what you and the IRS use to prepare and verify the return.2Internal Revenue Service. 2026 General Instructions for Forms W-2 and W-3 – Specific Instructions for Form W-2