[bombcar]

If I spent $5k as a business to realize $5k in revenue the tax is zero (ignoring as you say sales VAT, etc)

The problem comes when the $5k you “traded” also didn’t cover the actual expense to provide the $5k you “earned” - now you have an actual loss even if cash didn’t flow.

[gizmo686]

I could imagine somewhere trying to make that the rule, but I have a hard time imagining that rule being enforceable.

At least for US federal taxes, losses do not need to be tied to revenue. As long as they occur in the same tax year, you can deduct. You can also carryover losses to future years, or pass them through to personal income deductions; but the rules there get more complicated.

[bombcar]

Yeah from a tax standpoint you're fine, but from a "whole business cash-flow" concept you could end up in the hole even though on paper you traded $5k for $5k (accountants might have it booked somewhere as "goodwill" or something to make the books balance).