Most of your clients use the portal. A few don't: they want the client tax organizer in their mailbox, a paper copy of their return, and a Form 8879 they can sign at the kitchen table. That's three mailings a season, and each one has a different job and something different that has to come back.
Here's what the IRS says about each, how to mail a batch from one PDF per client, a cover letter to copy, and the record to keep. It's mailing structure, not tax or legal advice. In the template, {{double_braces}} are fields and [square brackets] are wording you write once.
Three tax-season mailings and what the IRS says about each#
None of the three has to go on paper, and all three can. Form 8879's instructions list U.S. mail beside email, fax and a website, both ways, and IRS Publication 1345 lets you give the copy of the return in any medium you and the client both accept. Paper is one of those media.
Three tax-season mailings and what each needs
Mailing | When it goes | Pages | What the IRS says about the medium | What has to come back |
|---|---|---|---|---|
Organizer kit (organizer, engagement letter, cover letter) | Usually early January, before you start returns | A full organizer can run 20 to 30 pages; a one-page checklist is the short version | Nothing: the organizer is your firm's own document. (The AICPA suggests sending it with the engagement letter, before you begin.) | The filled-in organizer or a note of what changed, the client's tax forms, and the signed engagement letter if you ask for one |
Copy of the return (often with your invoice) | When the return goes to the client to sign: February to April, and later for extension clients | Depends on the return | No later than when the return goes to the client for signature (IRC § 6107), in any medium you and the client both accept (Pub 1345) | Nothing. You keep a copy, or a list of names and taxpayer ID numbers, for three years |
Form 8879 | With the copy, before you e-file | One or two pages | Hand delivery, U.S. mail, private delivery, email, website or fax, in both directions (Form 8879 instructions) | The signed form, before you transmit. You keep it three years and don't send it to the IRS |
Where the official guidance lives (each checked October 14, 2026):
- Form 8879 and its instructions (opens in new tab) — how the form goes to the client and comes back, and that the return isn't transmitted until you have it signed.
- IRS Publication 1345 (opens in new tab) — keeping the signed 8879 for three years without sending it to the IRS (page 15), and giving the client a complete copy of the return in any medium you both accept (page 20).
- 26 U.S.C. § 6107 (opens in new tab) — a preparer gives the client a completed copy no later than when the return goes to them to sign, and keeps a copy or a list of names and ID numbers for three years.
- The AICPA's tax season prep guidance (opens in new tab) (December 22, 2025) — the organizer goes to the client with the engagement letter, before you begin.
How to mail each batch, one PDF per client#
One envelope is one PDF. Most tax software can save each client's organizer, or each client's copy of the return, as its own PDF (Drake Tax, for one, can save a PDF of each taxpayer's organizer to their Drake Documents folder). Before you upload, watch for two traps:
- Two files for one client. Some packages save the organizer and the engagement letter as separate files, and UltraTax CS has a setting that saves the client copies of the federal and state returns as separate PDFs. Combine each client's files into one PDF, cover letter first. Two uploads to the same client means two envelopes and two prices.
- One file for everyone. Some batch tools put every client in one file. Postmarkr mails a file to one address and doesn't split it, so every client's pages would go to one client.
Open each file before you upload it and check that it holds one client. Save it without a password, and test the run with two clients first. For prices, see what a mailed letter costs by page count.
The client tax organizer kit#
When each client's kit is different, such as an organizer filled in with last year's figures, use the Cart:
- Upload the client's PDF: cover letter, engagement letter, then the organizer.
- Choose the client from your address book, or type the address. It's checked against USPS address data before you pay. Mail returned as undeliverable because of an incorrect or incomplete address is not eligible for a refund or free resend.
- Read the preview. An address page comes first, placed to show through the envelope's windows, then every page of the kit as you saved it. Our print partner adds a small code strip in the bottom-left margin of every page, and black-and-white letters print in grayscale. Check that no other client's pages slipped in.
- Choose Add to Cart and repeat for the next client. You pay for up to ten together, so 60 clients is six checkouts.
- Pay by card with Send & Pay in your Cart. Printed the next business day.
Pay within six days of uploading a file, or upload it again.
When every client gets the same kit, such as a blank organizer or a one-page checklist, Bulk Send mails one shared PDF to up to 100 clients from a CSV. To put each client's name and return-by date on the letter, use a mail-merge template instead. A batch mails either one shared PDF or one merge letter, not both, so type a short checklist into the template rather than attaching an organizer.
Pages and price. A full organizer ran 20 to 30 pages when Accounting Today looked at organizers in 2007 (opens in new tab); condensed ones and checklists are shorter. One page in black and white costs $2.05 all-in, +$0.20 per extra page before the processing fee. The added address page counts as a sheet, and at seven sheets or more a letter travels flat in a Large envelope for +$2.50 before the fee. Double-sided printing keeps up to 11 pages in the standard #10 envelope: a 10-page kit is $3.91. A 20-page organizer is $8.54 either way, and a 30-page one $10.59. A PDF can hold up to 49 pages. Color printing costs more.
Postmarkr can't include a return envelope yet, so the cover letter tells clients how to send their papers back.
The copy of the return#
Save one PDF per client: the copy of the return, plus the Form 8879 and your invoice if they travel together. One preparer described the routine in 2008: return, bill and 8879 go out together, and the signed 8879 comes back by mail. An 8879 mailed on its own (two pages) is $2.26.
The copy carries Social Security numbers and bank details. Your documents are processed automatically. We never read or review the content of your mail. Each PDF prints as its own letter, and our print partner prints and mails it; see how we handle your documents.
Form 8879 for signature#
The slow part is the return leg. As with the organizer kit, there's no return envelope, so tell clients which of the IRS-listed routes your firm accepts: mail it back in their own envelope, drop it off, fax it or email a scan. If your software supports electronic signatures, that's one more route.
The 8879's instructions say the return isn't transmitted until you have the signed form, so count the round trip back from your deadline. The letter is printed the next business day, then USPS estimates 1–5 days for First-Class Mail, and once the client signs, their envelope makes the same trip back. More on how long First-Class Mail takes.
A tax-season mailing calendar#
Deadlines are the IRS's; the rest is most firms' habit.
- November to mid-December: a year-end letter to every client, if your firm sends one. It's a mail merge, like the retirement letter below.
- First two weeks of January: organizer kits.
- Late January: your bookkeeping clients' W-2s and 1099s go out; see how to mail W-2 forms and how to mail 1099 forms.
- Late January to the April deadline: the copy and the 8879 as each return is ready. Count back from the deadline for the 8879's round trip.
- After the April deadline: extension clients get the same pair before October 15, the extended filing date on the IRS extension page (opens in new tab).
Cover letter template for the organizer kit#
On the Cart route, fill in the fields yourself and save it as page one of each client's PDF. On the Bulk Send route, save it as a mail-merge template; the CSV needs the address columns plus one column for each field.
{{date}}
Dear {{salutation_name}}:
Your {{tax_year}} tax organizer is in this envelope,
with our engagement letter for this year's return.
Please send back by {{return_by_date}}:
- The organizer, filled in, or a note of what changed
- Your W-2s, 1099s and other tax forms (copies are fine)
- [The engagement letter, signed]
Mail them in your own envelope to the address below,
drop them at our office, or [fax or email a scan to:
firm fax or email].
When your return is ready, we'll send you a copy and
Form 8879 to sign. We can e-file only after we have
your signed 8879.
Questions? Call {{preparer_name}} at [firm phone].
Sincerely,
{{preparer_name}}
[Firm name, street address, city, state, ZIP]Replace the bracketed return routes with the ones your firm accepts, and make {{return_by_date}} a calendar date rather than "in two weeks", because arrival dates vary. This letter isn't an engagement letter: the AICPA's 2025 Individual Tax Return Engagement Letter – Form 1040 (opens in new tab) is a download for its Tax Section members.
What to keep, and what a mailing record can't show#
- The signed Form 8879, for three years from the return due date or the date the IRS received the return, whichever is later. Don't send it to the IRS unless it asks.
- A copy of each return, or a list of each client's name and taxpayer ID number, for three years after the close of the return period.
- For each letter you mail with Postmarkr, a PDF of exactly what printed, a status page with USPS scan updates when available, and emails when it's submitted for printing and when USPS reports it delivered or returned.
- Your own log of which 8879s came back, and when.
That record isn't a USPS Certificate of Mailing, a signature or a delivery receipt. It can't show that a client opened the envelope or that a signed 8879 is on its way back. If USPS confirms a letter was lost, we'll resend it for free.
Retirement and practice-sale letters to every client#
Once in a career, one letter goes to every client: you're retiring, selling the practice, merging or closing.
Where the official guidance lives: AICPA Code of Professional Conduct, ET 1.400.205 (opens in new tab) — before files move to a successor firm, a written request to each client for consent, which may be presumed after no fewer than 90 days without a reply; when a practice closes with no successor, written notice to each client (checked October 14, 2026). Check your state board of accountancy's rules too.
The mailing is a mail merge: one letter template with fields such as {{salutation_name}}, {{successor_firm}} and {{response_by_date}}, and a CSV with one row per client. Postmarkr's Bulk Send mails it to up to 100 clients per batch, so 250 clients is three batches, and each letter gets its own PDF of what printed and status page to keep with your records.
A disengagement letter to one client is a different job: the AICPA member insurance programs' site advises sending it by a traceable method that shows delivery and receipt (opens in new tab), so take it to a post office counter or a Certified Mail provider, and see what each USPS option records.
Questions about mailing tax documents to clients#
Can I mail Form 8879 and have it mailed back?#
Yes. The form's instructions list U.S. mail as a route both ways, beside hand delivery, private delivery, email, a website and fax, and the client returns it signed before you transmit. We don't include a return envelope yet, so the client uses their own.
Does the IRS require paper for any of this?#
No. The 8879's instructions list U.S. mail as one of six routes, Publication 1345 says the copy of the return can be in any medium you and the client both accept, and § 6107 sets a deadline for the copy, not a medium.
Does a paper organizer really cost $22 a client?#
That's Intuit's estimate, from an article arguing against paper organizers (opens in new tab) that was last modified July 28, 2016. It counts staff time as well as paper, printing and shipping. Mailing a kit through Postmarkr is priced by page count, from $2.05 for one page in black and white.
What if a client has moved since last season?#
Each address is checked against USPS data before you pay, so a flagged address is your cue to call the client and update it.
Can I mail to a client who lives outside the U.S.?#
Not with Postmarkr, which mails to U.S. addresses only. For a client abroad, use your portal or email, or mail it yourself at the post office.