It's called Allamagoosa and it's by Eric Frank Russell. Here is a plot summary from Wikipedia:
The story is set on board a military starship, the Bustler, but the tale is comic rather than heroic. The ship's officers and crew are facing an official inspection, and worry about having stores they should not have, or not having something that they should have. Checking, they discover that they are supposed to have an "offog", but no one has any idea what this is, so they create a bogus electronic gadget ("an imposing allamagoosa") and call it an offog to fool the inspecting admiral, pretending that it is a special device to measure the intensity of gravity fields.
As soon as they depart from the starport, they realize that it will be difficult to cheat a more experienced inspector in the future, so the offog must disappear from the inventory. Their great idea is to destroy it and report that it was broken. The captain sends an official report to the central command, explaining that the offog came apart under gravitational stress. Almost immediately, a message of maximum priority from the central command arrives: all starships must return to the nearest spaceport, Bustler included, for an immediate inspection.
Too late, the captain and crew learn that "offog" is a misprint for "off. dog," the ship's official dog, Peaslake, which has spent the whole course of the inventory making a conspicuous nuisance of itself. The animal's collar, drinking bowl, sleeping basket and (the unchewed half of) its cushion were correctly ticked off the inventory list without alerting the crew to their oversight. Obviously the central command is worried about how a dog could come apart, under gravitational stress or not.