PHOENIX (AP) _ Arizona is moving toward making online merchants collect sales tax on residents' purchases, a departure from the state's previous hands-office stance. The state Revenue Department has billed Amazon.com for $53 million in uncollected sales taxes for nearly five years. Amazon says it's contesting the state's assessment, which the company disclosed in its latest annual report. At the Legislature, Arizona lawmakers have introduced a bill to require Amazon.com and other retailers with distribution centers in the state to collect sales taxes. The bill is backed by brick-and-mortar retailers and it is scheduled for a hearing in one Senate committee but so far not in a second.