Remember that spelling rule you learned in elementary school about doubling the final consonant before adding -ed or -ing to a verb? Well, if you remember, then you know that there is a little more to the story.
When making a past tense or a present participle of a verb, we can’t just go doubling final consonants recklessly and assuming that all is right in the world of spelling; no, that would be too easy. Here’s the rule (oh that’s right, descriptivists, I said RULE): When a word of more than one syllable ends in a single consonant that is preceded by a single vowel, and the accent is on other than the last syllable of the root word, do NOT double the final consonant before adding the -ed or -ing. The final consonant in cancel is -l, which is preceded by the single vowel -e, and the accent is on the -can. The past tense of cancel, then, is canceled, and the participle is canceling.
There are, of course, exceptions to this rule—what would rules be without exceptions——-but cancel is not one of them. Oh, and neither is benefit, which I’ve also seen written as benefitted and benefitting; the correct spellings are benefited and benefiting. And that goes for travel, too; it’s traveled and traveling.
And now you know the rest of the story….