If you have sold your textbooks in foreign markets, foreign publishers may withhold foreign taxes at the source before the money is paid to your agent and before it is paid to you. If they are doing that, and you earned, for example, $10,000 in a foreign country, 10 percent, or $1,000, will have been withheld from your payment. Your agent would have received $9,000, and withheld his 15 percent commission on the $10,000 you actually earned. So you would end up getting about $7,500.