You may be able to apply the purchase price to the online product. But only customer service can do that. The online product is more expensive and has fewer features, so while Turbotax loves it as a money maker, I personally don't think anyone should use the online program unless they qualify for free filing.
However if you insist on using the online program and Costco won't take a return, you can either send the CD into Turbotax for the 60 day money back guarantee and then file online separately, or call customer support and ask if they can apply the CD cost to the online program.
The Satisfaction Guaranteed policy and claim form are here.
https://ttlc.intuit.com/replies/3301962
Customer support can be reached via Twitter, Facebook or telephone. https://www.facebook.com/turbotax/ and https://twitter.com/TeamTurboTax.
For telephone and other support options, see the instructions below.
https://ttlc.intuit.com/replies/3300041
