As everyone else’s taxes rise, one favored outfit may not have to pay federal taxes for years: General Motors. In another sweet deal from its benefactors on Pennsylvania Avenue, the government-owned car company is set to profit from billions of dollars in tax breaks not available to other businesses in the same predicament. The new GM will be allowed to claim a tax benefit from some $16 billion of net operating losses carried over from the old company, allowing it to avoid paying taxes on future profits, perhaps for years. The issue is a common accounting practice called “tax-loss carry...