Which spelling is correct: benefiting or benefitting?
Both spellings are considered to be correct; given the pattern of American English to prefer the shorter of alternate spellings (see color vs. colour; aluminum vs. aluminium), I would summarise that in the US the single-t version would be correct.
However, I see that the two-t version appears more often in searches, so it has popularity going for it.
Both are considered correct in the English language. Benefiting and benefitting both are acceptable due to two different English spelling rules.
If the final syllable is not accented/emphasized and it does not end in an l then you do not double the consonant. If you say ben-e-fit, you accent ben, the first syllable.
I believe it can become benefitting as well, due to the other English rule, that if a word ends with a short vowel followed by a consonant, you double the consonant so the vowel doesn’t become long.
Due to these two rules, I guess it can be spelled both ways.
Google found 12.900.000 (approximately) matches for benefiting , but only 1.210.000 for benefitting.
Merriam Webster lists both as correct spelling http://www.merriam-webster.com/dictionary/benefitting
Benefiting is the correct one in English and American English. There is no entry for 'benefitting' in the Cambridge dictionary, see: http://dictionary.cambridge.org/spellcheck/british/?q=Benefitting The reason being we double letters on the end of the word if that is where the emphasis lies. In 'benefit' the emphasis is on the 'n', rather than the last letter.