It could have a tail, if it got close enough to the Sun during it's brief passage through our solar system. The comet (apparently) originated outside the solar system, but it was observed while inside the solar system. If it had somehow been observed while still outside the solar system, no, it would not have had a tail then.
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..."Its true character became clearer after Karen Meech (University of Hawaii) recorded a series of images with the Very Large Telescope that, when stacked, showed a perfectly starlike object. So it's a deep-space asteroid, not a comet, and consequently officials at the MPC changed its designation to A/2017 U1."...
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