STOLEN GOODS - Don't expect any favors from Fences. Selling stolen items is going to cost you, so don't expect to get top dollar for ill-gotten goods. Tonila is exempt (actually all Thieves Guild & Dark Brotherhood fences are exempt, but in the vanilla game this just applies to Tonila). Any mod-added merchants who have been made members of the Thieves Guild or Dark Brotherhood faction will also be exempt. Options: -25% to -5% worse prices.
However, this isn’t always possible. For instance, you may have a $150 digital music player and want a small refrigerator worth $100. In this case, if both parties are certain of what they want and understand the difference in value, there should be no barterer’s remorse. Alternatively, you can ask for the mini-fridge plus $50 to make the trade – the worst anyone can say is “no.”
Put a price tag on it. Successful bartering must result in the satisfaction of both parties. This can only happen if the items bartered are realistically valued. If you have an item you would like to trade, obtain an accurate appraisal. An item is only worth what someone is willing to pay for it. Therefore, do your research and look at the "selling" section on eBay to find out what online buyers have paid for similar items.
INDEPENDENT ADJUSTMENT - One issue with adjusting the barter values is that these settings change both the Buy and Sell prices. This can make it difficult to find a nice balance if you're trying to lower your selling prices without making the buying prices ridiculously high. Personally, I really like the challenge created by being forced to sell my gear at greatly reduced rates, but I dislike the extreme inflation that occurs when I then want to buy something. Therefore, the Independent Adjustments will allow you to increase or decrease the buying & selling prices independently of one another. This is something I've not seen in any other mod, and in my opinion, it's one of the best, and most useful, features included in this mod.
Other countries, though, do not have the reporting requirement that the U.S. does concerning proceeds from barter transactions, but taxation is handled the same way as a cash transaction. If one barters for a profit, one pays the appropriate tax; if one generates a loss in the transaction, they have a loss. Bartering for business is also taxed accordingly as business income or business expense. Many barter exchanges require that one register as a business.
As Orlove noted, barter may occur in commercial economies, usually during periods of monetary crisis. During such a crisis, currency may be in short supply, or highly devalued through hyperinflation. In such cases, money ceases to be the universal medium of exchange or standard of value. Money may be in such short supply that it becomes an item of barter itself rather than the means of exchange. Barter may also occur when people cannot afford to keep money (as when hyperinflation quickly devalues it).