Basically, corporations have one place money comes in and two places it comes out, like so:
sales = expenses + profits
If you tax the sales, then deduct the expenses, that leaves the incidence of the tax on the profits. But importantly, unlike profits, it's usually clear to which country a sale belongs to.
Where this gets complicated is international borders, the solution there is to only deduct domestic expenses. At first that seems protectionist, but apparently changes to the currency exchange rates eventually balance out the effect and it ends up trade neutral.
This idea was actually seriously proposed a few years ago as part of a Republican tax reform initiative, and even economists like Paul Krugman seemed to think it checked out (who has a Nobel on trade, but is normally on the other side of the aisle). In the end it lost momentum after some big companies opposed it.
Even though that's maybe more ideal, just going for an agreement also seems reasonable since it's probably more achievable than in-depth reform (so it's likely solutions like this or nothing at least in the medium term).