The link in the answer by Sara@TurboTax is for Individuals. The question was for Incorporated Business. CRA DOES accept amended T2 returns by NetFile. According to CRA on this page:
http://www.cra-arc.gc.ca/tx/bsnss/tpcs/crprtns/ftr/rssssmnt/rqst-eng.html "You can electronically transmit a request for a reassessment to your corporation income tax return using the latest commercial tax preparation software packages."
It wouldn't work for me in TurboTax Inc. Bus., so I switched to TaxCycle, where it does work.
