Millions of immigrants benefiting from President Barack Obama’s executive actions could get a windfall from the IRS, a reversal of fortune after years of paying taxes to help fund government programs they were banned from receiving. Armed with new Social Security numbers, many of these immigrants who were living in the U.S. illegally will now be able to claim up to four years’ worth of tax credits designed to benefit the working poor. For big families, that’s a maximum of nearly $24,000, as long as they can document their earnings during those years. Some Republicans are labeling the payments “amnesty...