From the U.S. Postal Service announcement on November 17, 2020:
From the USPS: This Happy Birthday stamp conveys exuberant greetings by calling to mind the childhood excitement of a birthday party. Each of the five letters in the word “HAPPY” is inspired by a different party decoration in the midst of a flurry of multicolored ribbons and confetti. This stamp was designed by Lisa Catalone Castro and Rodolfo Castro, featuring a digital illustration by the latter. Ethel Kessler served as art director.
This stamp will be issued September 9th in Toast, N.C., but without a first-day ceremony.
The Scott catalogue number for this issue is 5635.
Additional information will be posted below the line, with the most recent at the top.
Updated August 25th:
Here are the first-day postmarks for this issue:
The Digital Color Postmark measures 2.54″ x 1.45″ 
The pictorial postmark measures 2.39″ x 1.15″
Updated July 30th from the Postal Bulletin:
On September 9, 2021, in Toast, NC, the United States Postal Service® will issue the Happy Birthday stamp (Forever® priced at the First-Class Mail® rate) in one design, in a pressure-sensitive adhesive (PSA) pane of 20 stamps (Item 577700). This stamp will go on sale nationwide September 9, 2021, and must not be sold or canceled before the first-day-of-issue.
This Happy Birthday stamp conveys exuberant greetings by calling to mind the childhood excitement of a birthday party. Each of the five letters in the word “HAPPY” is inspired by a different party decoration in the midst of a flurry of multicolored ribbons and confetti. Featuring a digital illustration by Rodolfo Castro, this stamp was designed by Lisa Catalone Castro and Rodolfo Castro. Ethel Kessler served as art director.
No automatic distribution.
How to Order the First-Day-of-Issue Postmark:
Customers have 120 days to obtain the first-day-of-issue postmark by mail. They may purchase new stamps at their local Post Office™ or at The Postal Store® website at usps.com/shop. They must affix the stamps to envelopes of their choice, address the envelopes (to themselves or others), and place them in a larger envelope addressed to:
FDOI – Happy Birthday Stamp
USPS Stamp Fulfillment Services
8300 NE Underground Drive, Suite 300
Kansas City, MO 64144-9900
After applying the first-day-of-issue postmark, the Postal Service™ will return the envelopes through the mail. There is no charge for the postmark up to a quantity of 50. There is a 5-cent charge for each additional postmark over 50. All orders must be postmarked by January 9, 2022.
Technical Specifications:
Issue: Happy Birthday Stamp
Item Number: 577700
Denomination & Type of Issue: First-Class Mail Forever
Format: Pane of 20 (1 design)
Series: N/A
Issue Date & City: September 9, 2021, Toast, NC 27049
Art Director: Ethel Kessler, Bethesda, MD
Designer: Lisa Catalone Castro, Bethesda, MD
Designer: Rodolfo Castro, Bethesda, MD
Illustrator: Rodolfo Castro, Bethesda, MD
Modeler: Joseph Sheeran
Manufacturing Process: Offset, Microprint
Printer: Ashton Potter (USA) Ltd. (APU)
Press Type: Muller A76
Stamps per Pane: 20
Print Quantity: 50,000,000 stamps
Paper Type: Nonphosphored Type III, Block Tag
Adhesive Type: Pressure-sensitive
Colors: Black, Cyan, Magenta, Yellow
Stamp Orientation: Horizontal
Image Area (w x h): 1.05 x 0.77 in. / 26.67 x 19.558 mm
Overall Size (w x h): 1.19 x 0.91 in. / 30.226 x 23.114 mm
Full Pane Size (w x h): 5.76 x 5.55 in. / 146.304 x 140.97 mm
Plate Size: 320 stamps per revolution
Plate Number: “P” followed by four (4) single digits in four corners
Marginal Markings:
Front: Plate number in four corners
Back: ©2020 USPS • USPS logo • Two barcodes (577700) • Plate position diagram (8) • Promotional text
Well, this one was scheduled for 2012, after celebrate stamps ran out.
Years ago they had a booklet of special occasions. A few of the occasions that I remember were birthdays, father’s day, mother’s day, etc. The problem was that in those days they weren’t Forever. I would like to see a booklet like that brought back as Forever stamps.
I remember those. They were issued from 1987 to 1988. There was no Father’s or Mother’s day related stamps. Just last year, the USPS issued Thank You set of 4 Forever stamps. There was also a Happy Birthday commemorate in 2002 (re-released in 2006 to meet the current rate). Later on, there was Celebrate issues from 2007 to 2009, which then followed by Forever Neon Celebrate in 2011 and 2015, respectively.
Wish these were being issued before the postage rate increase in August.
Has the postal rate been approved? I was under the impression it was just sent in for consideration…
As of 17 July, and the Broadcast/Availability of USA Philatelic 3rd Quarter, the PRICE of FOREVER stamps is still listed as 55c. How far back the Press Deadline was, I don’t know.
USPS# 577704 Pn-20 $11.00
nothing about the #06 Die Cut, or #08 No Die Cut press sheets for this stamp. #16 99c, #21 $1.70 ( No images for cancels )
About the Third Week in July, the FOREVER rate increase was approved. It has gone into effect. .55 -> .58 and others as well.