W-9 Request Letter to Vendors: What to Enclose, When to Send It and How to Mail It

A W-9 request letter asks a vendor to fill in, sign and return Form W-9 by a date you set. Send it with a blank W-9 behind the letter and your name and address already in the form's requester box, so the vendor can act from the envelope alone. If you've already asked by email or through your accounting software's invite, the paper letter is for the vendors who didn't answer.

This guide shows structure, not tax advice. In the template, {{double_braces}} mark details you fill in for each vendor and [square brackets] mark wording you write once.

What a W-9 request letter asks for and encloses#

The form carries its own instructions, so the letter only has to say what you need, by when, and how it comes back. Five things do the work:

• The ask: complete the W-9, enter the taxpayer identification number (TIN) in Part I, and sign and date Part II.
• The enclosure: Form W-9 (Rev. March 2024) runs six pages. Page 1 holds the form (the instructions start below it and run through page 6), and page 1 points the vendor to irs.gov/FormW9 for them. Enclose page 1, or all six.
• The requester box: before you save the PDF, type your business name and address into the box on page 1 labeled "Requester's name and address (optional)," so the vendor knows where the form goes back.
• A reply-by date: a calendar date, not "within two weeks."
• The return route: how the signed form gets back to you. Name the routes you already accept: your vendor portal or upload link, your fax number, or mail to your address in the vendor's own envelope.

Where the official guidance lives:

• About Form W-9 (opens in new tab) on IRS.gov — the current form, its revision and its instructions (checked October 14, 2026).
• Instructions for the Requester of Form W-9 (opens in new tab) — what you do with the form as the requester, including the conditions for taking W-9s electronically or by fax (checked October 14, 2026).

Two W-9 letters come with IRS rules about what goes in the envelope: the annual solicitation for a TIN that's still missing, and the B Notice. Read the section on them below before you mail either.

How to mail W-9 requests to vendors#

Each request goes out as one PDF: your letter first, the W-9 behind it. Open the IRS form, fill in the requester box, then print page 1 (or all six pages) to a new PDF, which keeps what you typed on the page. Combine that file with your letter in your PDF editor. Then pick the route that fits your list:

Every Postmarkr letter gets an added address page in front, printed with the vendor's address and your return address where they show through the #10 double-window envelope. So your letter needs no inside address, and the W-9 prints as you saved it, behind the letter. Our print partner adds a small code strip in the bottom-left margin of every page, and black-and-white letters print in grayscale. Each address is checked against USPS data before you pay. Printed the next business day.

Print single-sided if you want the form on a sheet of its own. In black and white, a one-page letter plus page 1 of the W-9 is $2.26. With all six W-9 pages, it's $5.86 single-sided, because the eight sheets (address page included) need a Large envelope, or $3.29 double-sided. Each price includes printing, the envelope, the address page, USPS First-Class postage and the processing fee, and it's the same for one vendor or a hundred. Prices for other page counts are on our invoice mailing page for finance teams.

Return envelopes aren't available yet, so your letter's return line does that job; a vendor who mails the form back uses their own envelope. Postmarkr envelopes can't carry a custom marking either, which is why the annual solicitation and the B Notice, below, are letters to mail yourself.

When to send W-9 requests before 1099 season#

Mail the paper request as soon as an email request has gone unanswered. Count the mail both ways: USPS estimates 1–5 days (opens in new tab) for First-Class delivery, and a form mailed back needs that time again. A request mailed in November or the first week of December leaves room for a reply-by date about two weeks out, one follow-up, and the form's trip back before you prepare 1099s in January.

Where the official guidance lives: Instructions for Forms 1099-MISC and 1099-NEC (opens in new tab) (Rev. December 2026) — which payments are reported, the $2,000 reporting threshold for tax years beginning after 2025, and the January 31 filing date (checked October 14, 2026).

Once the W-9s are back, our guide to mailing 1099 forms to contractors covers which pages go in each envelope and when to send them.

W-9 request letter template#

Use one letter for the first paper request and for the reminder. For a vendor whose details may have changed, use the bracketed updating paragraph in place of the first one. Delete every bracketed alternative you don't use.

{{date}}

Re: Form W-9 for {{vendor_name}}
Vendor number: {{vendor_id}}

Dear {{salutation_name}}:

We need a signed Form W-9 from {{vendor_name}} for
our {{tax_year}} tax reporting. Please send it by
{{reply_by_date}}.

[Updating a W-9? Use instead: The W-9 we have for
you is from {{w9_on_file_year}}. If your name,
address or tax classification has changed since
then, please send a new one by {{reply_by_date}}.]

A blank Form W-9 is enclosed, with our name and
address in its requester box. [No enclosure? Use
instead: You can download the form at
irs.gov/FormW9.]

Please return the signed form [through our vendor
portal at link / by fax to number / by mail to
address].

Already sent one, or have a question? Call [name] at
[phone].

Thank you,

{{sender_name}}
[Company name], Accounts Payable

Enclosure: Form W-9 (Rev. March 2024)

There's no inside address because Postmarkr prints the vendor's address on the page it adds; if you mail it yourself, add it above the salutation. As a Bulk Send letter template, the letter can't carry the W-9, so use the download line, delete the "Enclosure" line, and fill every field for every vendor in your spreadsheet. For the shared-PDF route, replace each {{…}} field with general wording, such as "Dear vendor," before you save the PDF. How templates and mail merge work covers the spreadsheet setup.

Annual solicitations and B Notices: different envelope rules#

The IRS defines two W-9 letters of its own and says what goes in each envelope. Each publication says when its letter is due; the table gives the one-line version, and the links below give the rest.

If your letter is one of these, mail it yourself so the envelope holds what the publication lists. For an annual solicitation, that's your letter, the W-9 and a return envelope; Publication 1586 also describes making the request by telephone. For a First B Notice, it's the notice and the W-9 in an outer envelope with the marking.

Where the official guidance lives:

• IRS Publication 1586 (opens in new tab) — when first requests and annual solicitations for a missing TIN are due, and what a mailed annual solicitation must include (checked October 14, 2026).
• IRS Publication 1281 (opens in new tab) — when a B Notice is due after an IRS CP2100 or CP2100A notice, the notice texts and the envelope marking (checked October 14, 2026).

What to keep from each W-9 request#

• The mailing record. For a Postmarkr letter, that's the PDF of exactly what was printed, letter and W-9 together, and its page in Sent, with dated updates and USPS scans when available. For a letter you mailed yourself, keep a copy of what went in the envelope.
• The dates: the day you mailed it and the reply-by date you gave.
• The reply: how and when the W-9 came back.
• The signed W-9, filed with the vendor's record.

That record shows what you sent and its progress; it isn't a Certificate of Mailing. If a letter comes back undeliverable, find a current address and send it again. Mail returned as undeliverable because of an incorrect or incomplete address is not eligible for a refund or free resend.

Questions about W-9 request letters#

Can I email a W-9 request instead of mailing it?#

Yes. IRS Publication 1586 says a first request for a TIN can be made orally, in writing or electronically. The mailed letter is for the vendor who didn't answer the email. Either way, give a return route other than a plain email reply, such as your portal, fax number or mailing address, because the completed form carries their TIN.

How does the vendor send the W-9 back without a return envelope?#

By the route your letter names: your portal or upload link, your fax number, or mail in their own envelope to your address. The annual solicitation is the one W-9 letter whose mailed version includes a return envelope; see the section on it above.

Do I send the completed W-9 to the IRS?#

No. The form's own header says "Give form to the requester. Do not send to the IRS." Keep the signed form with the vendor's record.

What if a vendor never sends the W-9 back?#

Two IRS sources cover it. The IRS backup withholding page (opens in new tab) explains when a payer has to withhold 24% from future payments, including when a payee hasn't provided a correct TIN, and Publication 1586 (opens in new tab) sets out the follow-up requests and their dates.

Does the address on the W-9 become the 1099 address?#

The requester instructions say to show "the full name and address as provided on Form W-9" on the information return and on the payee's copy, and to update your records if the payee marks their address "NEW." If a 1099 later comes back, our 1099 guide covers what to do when an envelope comes back.