Hi Matt,
Gross proceeds cannot be negative, as they are just the sum of all of your fair market values at the time of each sell or trade to another cryptocurrency. You can wind up with a negative gain when the gross cost basis is larger than the gross proceeds. This is quite common.
You can also automatically build out your required cryptocurrency tax reports by using one of TurboTax's cryptocurrency partners. The software will allow you to import all of your trades and will automatically do all of the number crunching for you.
