Too often a translator of Japanese to English will complete a perfectly good translation and then deliver it to a customer without a careful spell-check.
The spell-checker installed as part of word-processing software in computers is fairly reliable, and a translator should acquire the habit of always running the program after completing a translation. Remember, though, that running an automated spell-check on a translation is not enough by itself.
A spell-check only catches misspellings (and double occurrences of words, such as "the the," and will pass over correctly spelled words used incorrectly. An example is the word "than" in "Drink the medicine, and than rest." The word before "rest," of course, should be "then." The spell-checker reads "than" as correctly spelled -- which it is; it just happens to be the wrong word.