Watching Willie Nelson and Family put the finishing touches on a sold-out, four-night stand at the Fillmore in San Francisco on Thursday night, one couldn't help but recall that the deadline for Americans to file their yearly tax returns is just two months away.

Nelson, the 69-year-old country legend whose songbook borrows from the traditions of classic pop, honky tonk, Western swing, jazz, rock and the blues, is no stranger to IRS procedure. In 1990, the Texas native was slapped with a bill for $16.7 million in back taxes. He subsequently lost almost all of his assets -- including houses, farms, recording studios and musical equipment -- and ultimately paid off his massive debt with the proceeds from 1992's The IRS Tapes: Who'll Buy My Memories? a 25-track collection of demos, outtakes and rarities.

These days, Nelson is on the road again -- as he has been for much of the past decade, recouping his fortune through an endless series of tours and a steady stream of new albums, from 1996's uneven Spirit to 2002's ambitious, albeit supremely muddled Great Divide.

Wrapping up a successful Bay Area stop on his Great Divide Tour, Nelson sauntered onto the Fillmore stage, decked out in his signature red bandana, faded black jeans, a black t-shirt and black sneakers. Set against the backdrop of a giant Texan flag, his braided locks flowing nearly to his waist, he looked nothing like the clean-cut, sharply dressed young man who arrived in Nashville in 1961 to try his hand as a country crooner. But he sounded just as spry, his nasally voice just as bold and distinct in 2003 as it was on his 1962 Liberty Records debut, And Then I Wrote.

Backed by his longtime Family members -- guitarists Jody Payne and Jackie King, bassist Bee Spears, pianist Bobbie Nelson, harmonica whiz Mickey Raphael and drummers Billy and Paul English -- the aging troubadour casually launched into a robust, two-and-a-half-hour set filled with original hits ("On the Road Again"), timeless standards (Irving Berlin's "Blue Skies," Hoagy Carmichael's "Georgia on My Mind") and choice country classics (Patsy Cline's "Crazy," Townes Van Zandt's "Pancho and Lefty"). Along the way, he paused to down a shot (compliments of one generous fan), shower his audience with tokens of his appreciation and share brief embraces with his supporting players.

An outspoken champion of the National Organization for the Reform of Marijuana Laws, Nelson was greeted by the familiar odor of burning joints as soon as he took the stage. From the moment the lights went down, a thick cloud of smoke rose steadily from the capacity crowd of 1,100, a diverse mix of young fans, middle-aged devotees and Bay Area cowhands. (Even so, the audience boasted only twice as many cowboy hats as the band, by a count of six to three.)

Nelson responded in kind to his reveling followers, wasting little time in pulling out concert staples like "Always on My Mind," "Mama Dont Let Your Babies Grow Up to Be Cowboys" and the Steve Goodman chestnut "City of New Orleans." Following an up-tempo, honky-tonk take on Kris Kristofferson's "Me and Bobby McGee," he even ceded the mike to Payne for a rollicking rendition of "Working Man Blues," which found Nelson and his fellow guitarist exchanging rugged chops and intricately woven solos.

Throughout the evening, Nelson commanded the stage with the cool confidence of a road-weary veteran, effortlessly bridging the transitions from song to song with a clever lick or a quick quip and daring his fans to keep pace. By the time he went electric at the two-hour mark for a riveting jam with Payne and Raphael, Nelson had long since proven that time has taken none of the spring out of his musical step.

Closing out the night with a tribute to Hank Williams Sr., a soulful "Amazing Grace" and "The Party's Over," the somber ballad that has long provided a fitting swan song to Nelson's shows, the country outlaw stayed true to his country roots, much to the delight of fans who roared their approval.

By now, his Bay Area followers have seen this act before -- Nelson's February shows at the Fillmore have practically become an annual rite of winter, and his mellow stage demeanor hasn't changed in decades. Yet his appeal endures, not simply because of his status as one of country's living legends, but because he can still play like one.