You can't "write off" the uncollected amount unless you do your accounting on an accrual basis, which means that you count the income when you bill it.  Rather, most abstractors (myself included) do their accounting with the more simple cash basis method, which means you don't count it as income until you get the check.

Put more simply, you cannot write off a uncollected debt against monies you have collected.  You pay the tax on the amount you actually receive in either manner, it is just a matter of when you factor it in. 

Best,
Robert A. Franco
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