“You must pay taxes. But there’s no law that says you gotta leave a tip”

Morgan Stanley (an American multinational financial services corporation) ran an advertisement in 2006 that featured a memorable line:
 
“You must pay taxes. But there’s no law that says you gotta leave a tip.”
 
The advertisement’s tagline has been included in many collections of one-line sayings about taxes.
 
 
Wikipedia: Morgan Stanley
Morgan Stanley (NYSE: MS) is an American multinational financial services corporation headquartered in the Morgan Stanley Building, Midtown Manhattan, New York City. Morgan Stanley operates in 42 countries and has more than 1300 offices and 60,000 employees. According to the Scorpio Partnership Global Private Banking Benchmark the company had 1,454 USD Bn of assets under management (AuM) in 2014, an increase of 17.5% on the 2013 figure.
   
Google Books
Real Estate Tax Secrets of the Rich:
Big-Time Tax Advantages of Buying, Selling, and Owning Real Estate
By Sandy Botkin
New York, NY: McGraw Hill Professional
2006  
Pg. 171:
You must pay taxes. But there is no law that says that you gotta leave a tip. —Advertisement
 
Google Books
One-Income Household:
How to Do a Lot with a Little
By Susan Reynolds and Lauren Bakken
Avon, MA: Adams Media
2009
Pg. 164:
After all, as an advertisement for Morgan Stanley (a financial investment firm) once touted, “You must pay taxes. But there’s no law that says you gotta leave a tip.”
 
Twitter
Michael Fry
‏@MichaelFry
“You must pay taxes. But there’s no law that says you gotta leave a tip.”
1:28 PM - 15 Apr 2009
   
Forbes.com
9/20/2013 @ 11:57AM 20,161 views
20 Inspirational Quotes ... About Taxes
By Robert W. Wood
(...)
4. “You must pay taxes. But there’s no law that says you gotta leave a tip.”–Morgan Stanley advertisement
 
Twitter
TurboTax Canada
‏@TurboTaxCanada
You do have to pay taxes, but no one says you have to leave a tip. #TaxTruths (paraphrasing Morgan Stanley)
8:47 PM - 24 Apr 2014
 
Twitter
Bruces` tax tweet
‏@bruce_taxguy
“You must pay taxes. But there’s no law that says you gotta leave a tip.”
5:15 PM - 21 Mar 2015