The only place I've seen acceptance be a problem is San Francisco (although I've certainly heard it's a problem in other American cities). I can't speak to other cities but in San Francisco the cabbies are required to pay pretty hefty fees for credit card usage. But Uber and Lyft take a big chunk of the pie and leave no cash option so there's that.

I've been to a couple cities where credit cards were not accepted as a general rule (cabbies didn't even have the equipment). But in cities where I've used a card I've asked and generally been told they'd never do anything that ridiculous. Of course I typically have a strong preference for public transit so cab rides are the exception rather than the rule for me.

As for accounting, merchants already get a category assigned to them by their credit card processor. Generally there's enough specificity that something like a few cab rides shouldn't need much more clarification (although receipts may be required if you cross a threshold or exhibit some suspicious pattern).