Enlarge By Chris Hawley, USA TODAY Diego Rivera used his "Containing the Ice of the Danube in Bratislava," left, in the Mexico City's Ministry of Finance museum, to pay his taxes.

That's the deal Mexico has offered to artists since 1957, quietly amassing a modern art collection that would make most museum curators swoon. As the 2009 tax deadline approaches, tax collectors are getting ready to receive a whole new crop of masterworks.

"It's really an amazing concept," says José San Cristóbal Larrea, director of the program. "We're helping out artists while building a cultural inheritance for the country."

There's a sliding scale: If you sell five artworks in a year, you must give the government one. Sell 21 pieces, the government gets six. A 10-member jury of artists ensures that no one tries to unload junk.

Under the program, the Ministry of Finance and Public Credit now owns 4,248 paintings, sculptures, engravings and photographs by Diego Rivera, Rufino Tamayo, Leonora Carrington and other masters.

The government displays these treasures in Mexican museums and government offices and, increasingly, loans them out for special exhibitions around the world. Other works are stored in a huge, climate-controlled warehouse in Mexico City.

Clerks dutifully post each artwork on the tax office website, and the agency hangs them proudly in its own museum in downtown Mexico City. (Visitors to the website can see what each artist has given each year. Click on "Colecciones Pago en Especie" at apartados.hacienda.gob.mx/cultura/index.html).

Some of the art is explicit, but no matter.

"There's no censorship here," says Julieta Ruiz, a curator at the museum.

If anything, the temptation to needle the taxman makes the art even edgier, she says.

Rafael Coronel's 1980 tax payment is a portrait called He Who Doesn't Pay Taxes. A painting that Fabian Ugalde contributed in 2002 declares in huge letters, "The authorities have still not determined whether it was an act of aggression or just another piece of art."

A 10-foot-high drawing by Demián Flores shows a man sexually assaulted by a rattlesnake, an apparent reference to the Mexican government because the rattlesnake appears on the Mexican flag.

The art program was the idea of two muralists, David Alfaro Siqueiros and Gerardo "Dr. Atl" Murillo. In 1957, an artist friend of theirs was about to go to jail over tax debts so the two men approached Mexico's tax director and talked him into an art-for-amnesty deal.

Soon the tax office was accepting original art on a regular basis. In 1975, the Payment in Kind Program became an official part of the tax code.

Not everyone can pay with art. Participants must register with the Tax Administration Service, Mexico's version of the Internal Revenue Service, by submitting a body of their work to the jury and proving they have shown or sold artworks.

About 700 artists are registered, though not all of them pay with art every year, San Cristóbal says.

Most pieces pass muster, but a few well-known artists have had their contributions rejected in recent years, San Cristóbal says. He declines to name names.

The program is only for visual art, not music or literature. Administrators may soon accept performance art as well, San Cristóbal says. Artists would have to submit videos, photographs or other artifacts of their performance that the government could store and display, he says.

The collected artworks are divided equally among the federal government, Mexico's state governments and its municipal governments.

Many have soared in value since the artists handed them over. A piece by Diego Rivera that was valued at $50,000 in the late 1950s is now worth millions of dollars, San Cristóbal says.

By law, however, the government cannot sell any artworks from the collection. The artworks become protected "cultural heritage objects," but there is also a more practical reason: If the government made a profit, it would have to give the artists a tax refund, San Cristóbal notes.

Asked which contemporary artists he would like to add to the tax office's collection, San Cristóbal's eyes lit up.

"Oh, I'd love to have a Gabriel Orozco," he says, referring to one of the country's hottest sculpture and installation artists. Then he sighs.

"Orozco lives in New York now. He pays American taxes."

Hawley is Latin America correspondent for USA TODAY and The Arizona Republic