“If you need it, we have it” is a business slogan that has been advertised since at least 1907. “If we don’t have it, you don’t need it” is a business slogan that has been advertised since at least 1949.
 
In 1955, it was reported that one business displayed a “If you need it, we have it” sign, and a business across the street posted the other sign, “If we don’t have it, you don’t need it.”
 
“If it’s in stock we have it, and if we ain’t got it, you don’t need it” was printed in a 1968 newspaper. “If it’s in stock, we have it” is a popular related saying.
 
   
1 January 1907, Dallas (TX) Morning News, pg. 15, col. 4 ad:
PALACE DRUG STORE
IF YOU NEED IT WE HAVE IT.
 
14 October 1907, Baltimore (MD) American, pg. 6, cl. 6 ad:
If You Need It, We Have It!
SOUTHERN ART CO.
 
10 June 1949, The Daily Olympian (Olympia, WA), pg. 3, col. 7 ad:
“LAZY LOU”
IF WE DON’T HAVE IT—YOU DON’T NEED IT
 
16 June 1952, The Register-News (Mt. Vernon, IL), pg. 12, col. 6 ad:
Again we are going to say, if we don’t have it, you don’t need it.
Why?
Vacuum Cleaners
Are Our Only Business
O. R. BUFORD
 
30 May 1955, The Daily Chronicle (Centralia, WA), “The Monday Tattler,” pg. 3, col. 3:
John Millman postcards from Winlock that a local store posted this sign in its window the past week: “If you need it, we have it.” Across the street a competitor flashed back: “If we don’t have it, you don’t need it.”
 
Old Fulton NY Post Cards
21 February 1957, Belmont (NY) Dispatch, pg. 5, col. 4:
Signs of the times: In the window of a department store—“If you need it, we have it.” In the window of another store across the street—“If we don’t have it, you don’t need it!”
 
1 March 1957, Omaha (NE) World-Herald, “The Nebraska Scene” by Bill Dunn, pg. 27, cols. 2-3:
E. R. Montgomery, publisher of the Morrlll Mail, was amused by competition in signs. The first: ‘If you need it, we have it.” The second, in a firm across the street: “If we don’t have it, you don’t need it.”
 
Google Books
October 1965, The Rotarian, pg. 65, col. 2:
The manager of a department store put this notice in the window: “If you need it, we have it.”
 
But in the window of a rival, a sign appeared stating, “If we don’t have it, you don’t need it.” — Wheel Chatter, Santa Paula, California.
   
23 September 1968, Minneapolis (MN) Tribune, pg. 22, col. 5 photo caption:
‘IF IT’S IN STOCK WE HAVE IT, AND IF WE AIN’T GOT IT, YOU DON’T NEED IT’
So says a sign at Acme Electronics, which sells everything from TV tubes to potentiometers
 
Google Books
The Comic Encyclopedia:
A Library of the Literature and History of Humor Containing Thousands of Gags, Sayings, and Stories
By Evan Esar
Garden City, NY: Doubleday
1978
Pg. 226:
The manager of a variety store put this notice in the window: If You Need It, We Have It.
 
In the window of a rival store on the next block a sign appeared: If We Don’t Have It, You Don’t Need It.
     
The Huffington Post
February 13, 2015
New York Originals
Frank Bee, Throg’s Neck, Bronx
Originally started in 1957, this five and dime store sells all manners of housewares and necessities yet their motto is “if we don’t have it, you don’t need it.”