Few PDFs get filled out as often in the United States as the W-9 and the W-4. A new client wants a W-9 before they pay you, a new employer hands you a W-4 on day one, and both ask for the one number you should never casually hand out: your Social Security number. These forms are fillable and short, so the form itself is rarely the problem. The mistakes happen around it: using an outdated version, sending it to the wrong place, or emailing an SSN in the clear. This guide walks through the most common work forms and how to handle them. It is general information, not tax advice, so check with a tax professional for your own situation.
Start with the official, current version
Government forms are revised from time to time, and a form from an old email may be out of date. Download a fresh copy from the agency that publishes it, for example the Forms and Instructions page at irs.gov, or the Form I-9 page at uscis.gov. Look for the revision date printed at the bottom of the first page.
Avoid third-party sites that offer the form after a signup or ask for payment. The official versions are free. Also be wary of anyone who emails you a "W-9" attachment and asks for it urgently, since that is a common scam. Confirm the request by calling a number you found yourself.
What a W-9 is, and who gets it
The W-9 is the Request for Taxpayer Identification Number and Certification. Freelancers, contractors, landlords and anyone who is paid as a non-employee are commonly asked for one. You give the completed form to the person or company that asked for it, not to the IRS. They use it to report what they paid you.
To fill it in:
- Open Fill PDF Form and add the downloaded W-9.
- Line 1: your name as it appears on your tax return. Line 2: a business name or DBA, only if different.
- Line 3: tick your federal tax classification, such as individual or sole proprietor, or an LLC or corporation type if that applies.
- Address and city, state and ZIP: your mailing address.
- Part I: enter either your Social Security number or your Employer Identification Number, not both. Sole proprietors can often use an EIN if they have one, which keeps their SSN off the form.
- Part II: sign and date. Use Sign PDF for the signature.
Use the form's own instructions for lines that do not fit your case. A tax classification chosen incorrectly can cause trouble later, which is where a short question to an accountant is cheap.
The W-4 is different
The W-4 is the Employee's Withholding Certificate. It tells your employer how much federal income tax to hold back from each paycheck. You hand it to your employer or payroll department, not to the IRS.
The IRS publishes a new version each year (the 2026 form is current at the time of writing), and the layout has five steps. Only Step 1 (personal details) and Step 5 (signature) are required. Steps 2 to 4 are there for people with more than one job, dependents, or other adjustments. If your situation is simple, you can fill in Step 1, sign Step 5 and stop. If it is not, the IRS provides a Tax Withholding Estimator on its website that walks you through the numbers. You can submit a new W-4 to your employer whenever your circumstances change.
The I-9 has a split job
Form I-9 verifies that you can work in the United States. You complete Section 1 yourself, no later than your first day of work. Your employer then completes Section 2 after reviewing your original identity documents, which has to happen within a few business days of your start date. Employers are the ones who retain the form, and the documents you show are your own to choose from the official list.
Because the employer must examine documents in person or through an approved process, do not email photos of your passport or driver's license unless your employer specifically asks for them through a secure method. Ask how they want to verify them.
Send your SSN safely
These forms are exactly where identity theft starts, so the delivery matters as much as the answers.
- Fill the form on your device. A tool that runs in your browser, as ours does, never uploads the file. See how to check that an online PDF tool is private.
- Use the secure portal your client or employer offers. Many payroll and accounting systems have one.
- If email is the only choice, add a password with Protect PDF and tell the recipient the password by text message or phone call.
- Do not post or share the form in a public chat or an open document link.
- Ask whether you can use an EIN instead of your SSN if you run a business, or whether the other party only needs the last four digits for their records.
When you later share a document that includes the completed form, for example a bank statement or tax return, learn how to hide the number with our guide to redacting a PDF properly.
Flatten, name and keep a copy
Before you send, tick Flatten the form in Fill PDF Form so your answers become part of the page and cannot be edited by accident. Give the file a clear name such as W-9-Jordan-Lee-2026.pdf, and save a copy in a folder you will remember. If you are ever asked what you sent, or need to send it again to another client, you will have it.
Not sure if the file you got is the fillable kind? Our general guide to filling out a PDF form explains how to tell, and what to do when it is not.
Other forms you may meet
The same steps apply to many other common documents: rental applications, school registration, medical intake sheets, direct deposit forms and permission slips. Download the latest version, fill it on your device, flatten the final copy, protect it if it travels by email and keep a record. If a landlord or lender asks for supporting documents as well, put everything in order with the steps in our guide to rental and mortgage application documents.
