I've read where the IRS will try to enforce the "real market value" of a service and require you to pay tax on it. I'm wondering how enforceable this is, and if you can get around it if its less than $500 in value or if you declare that it is a "donated service" on each side.
https://www.irs.gov/uac/four-things-to-know-about-bartering-1
Two people exchanging goods or services on a commercial basis and then pretending it was two gifts is tax evasion. It's not a gift. It's a commercial sale that you lie about by 'putting' a different 'label' on it.
Sometimes two people will give mutual gifts, e.g. if you come to my wedding: I give you dinner, you give me some kitchenware. Yet there's nothing commercial about it. So that's not income for either party.
However, if you're talking about two businesses making sales to each other, that is very much income, regardless of what you badge it.
If the services are less than $500 in value, they don't have to be reported.
As regarding "donations," there needs to be some kind of a "gift" element involved. The maximum excludable amount for gifts is $11,000.
I am not a lawyer or tax adviser, so see a person that is qualified in these matters.
