Gov. Nikki Haley has until midnight Tuesday to sign or veto the deal approved by lawmakers last week. Spokesman Rob Godfrey says she will do neither. That allows it to become law without her signature.
The Republican governor opposed the deal but repeatedly said she would not veto it.
The measure says Amazon doesn't have to collect sales tax from South Carolina's online shoppers until January 2016. In return, the company promises to create 2,000 full-time jobs with health benefits and invest $125 million.
Amazon has said its plans to build a distribution center in Lexington County will resume when the bill becomes law.