Earlier sessions at Abbey Road Studios in early 1972 included "Left Handed Luke", "Country Honey", "Electric Slim & the Factory Hen", also "The Groover" and "Blackjack" but these versions were not featured on any original studio album. The earlier Abbey Road sessions were either shelved or destroyed, and those songs would be re-recorded at Strawberry studios. The early sessions of "Blackjack" and "The Groover" are featured on The 20th Century Superstar box set.
Tanx was released on 28 January 1973 by record label EMI in the UK and Reprise in the US.
Tanx was a hit in UK and Europe but it failed to match the success of The Slider in the US, reaching only No. 102 in the album charts.
Curiously, the popular single "20th Century Boy" was not included on the album, which may have affected sales, as the album (unlike its two predecessors) did not include a hit single.
The album is also widely known to be the last of T. Rex's string of successes since Electric Warrior; their next album Zinc Alloy and the Hidden Riders of Tomorrow would prove to be a financial failure and put Bolan's musical career in jeopardy until 1976. It's also T. Rex's last album released under Reprise Records in the US, as Light of Love, released under Casablanca Records (like Reprise, distributed through Warner Bros. Records), would be the last of their albums released in the US.
Tanx was remastered for CD by Edsel Records in 1994 as part of their extensive T. Rex reissue campaign. A number of bonus tracks were added (see below). A companion release, entitled Left Hand Luke (The Alternative Tanx), was released in 1995 and contained alternative versions, studio rough mixes and demos of the main album and bonus tracks. A combined album digipak was released in 2002.
In 2003, further recordings from the Tanx sessions were released by Thunderwing Productions Limited (TPL), the owners of several original ¼", 1" and 2" Master Tape recordings of Marc Bolan & T. Rex. These tracks were released as The Tanx Recordings.
At the time, Tanx was critically derided by journalists as an uneven departure from the unique melodic rock and roll that made the band famous. Paul Gambaccini of Rolling Stone wrote "This one album might have made a good EP, since there are four worthwhile tracks, but the remaining nine are flights of Bolan's fantasies that might be interesting to his numerous devotees but less so to more casual listeners", calling it "a sad indication that Bolan really hasn't progressed and I can't see many people being truly pleased with it. But I've been wrong before."
Retrospective reviews have been more favourable. Whitney Strub of PopMatters wrote "One reason for Tanx's commercial failure was its lack of the immediacy for which glam was known. [...] But what doomed the album on the charts is precisely what earns it reinspection today: the songs, for the most part, flow cohesively from one fractured mini-narrative to the next". Stephen M. Deusner of Pitchfork, whilst praising the record, called it "a difficult album".