Great question! I guess we should avoid all legal questions ideally and simply rely on incentives.  

 Depends on the country, but in Slovakia, if the unit is the same, then it's not selling, just changing form. That is one of the best use-cases for Monero in entrepreneurship.

Say you want to have a Bitcoin reserve in a company, but also want to pay suppliers with some crypto. Sale is a taxable event that goes to weighted average and triggers capital gains. So actually buying Monero and spending it at the same moment is a tax free event (buy and sale price are the same, minus the fees), but doing it with anything Bitcoin (does not matter if Cashu/fedi/lightning) would be taxable event. Of course you can also use stablecoins. 

 You mean like doing a swap from bitcoin to monero and having that monero being send to the person you are paying? Doesn't that count as a sale and trigger cap gains?  

 no, swap fiat to monero, just to not have to use banks for payments. 

selling bitcoin would be a tax event. buying something else and then immediately using it all to pay an invoice is tax zero. 

so you can both save Bitcoin as a company and use advanced third millennium payment technologies (i.e. Not legacy camping system) 

 Ah you buy just the right amount of monero at an exchange (plus a bit for fees) and send that to the person you are paying? Could also keep a balance in a stablecoin and swap what you need to monero then. 

 no, you can't. at least not legally without tax in most countries. 

if you don't want to pay tax, there needs to be no capital gain, so the exchange rate has to be the same. you have to buy and use all the monero for payment, holding zero at any moment. 

 Yes, I was referring to holding stables and swapping that to monero and then spending all of the monero. 

 That only works if your there is a stablecoin that is the same denomination in your company's accounting currency.  

 Right. Makes sense.