>>>>> Tenants of a rental property improve the property. The cost[..,.]
>>>>>> of labor plus materials is $6000. Their landlord pays them
>>>>>> for the improvements by forgiving $6000 in rent payments.
>>>>> However, it seems that the landlord is getting to count the[...]
>>>>>> $6000 as a deduction twice. First, he is obviously
>>>>>> deducting the $6000 as a maintenance or capital improvement
>>>>>> expense, or else he would not have issued the 1099-MISC.
>>>>>> Second, since he received $6000 less in rental receipts we
>>>>>> are assuming that he did not record as income the $6000 he
>>>>>> did not receive.
I'm not sure the OP was clear on this point. But are/is the lessee
> actually in business and renting business premises from the lessor? >
> That's the impression I got anyway.
I assumed they were residential tenants and the landlord in a passive rental activity. I also assumed that this deal was agreed-to in advance via an arm's-length transaction.
But regardless of business vs. residential, and regardless of what kind of 1099 was or was not issued, the tenants received $6K rental value for doing something they anticipated would cost them less than $6K to provide -- otherwise, why would they do it? I use "cost" here in the economic sense, not the tax sense.
Therefore they have gross income of $6K in a for-profit activity and owe taxes on the net profit. If they totally miscalculated and have legitimate expenses (for example, accidental breakage) that actually exceed $6K, they would have a business loss (which might inspire them to close up shop and never try that business again).
But for the month or two they did the work, they were in business (or else they were employees of the landlord, but let's not go there).
The landlord also received $6K rental income, against which he can deduct some combination of repair expenses and depreciable capital improvements which add up to $6K (so, no, he is not double dipping).
It was a barter exchange. See the first two paragraphs under "Bartering" and Example 4 on page 18 of 2007 Pub 525, which is almost exactly this same scenario. In Example 4, the tenant is an artist, which could be either a hobby or a business. It seems unlikely to me that the tenants in our example do this kind of thing as a hobby.
-Mark Bole