Amazon sellers owing an estimated $2 billion in uncollected sales taxes are being offered the chance to waive those obligations as part of a new multi-state agreement.

Thirteen states came together on Wednesday to announce a new sales tax amnesty program for online merchants who sell on Amazon and other sites. For three months starting Aug. 17, sellers with potential tax liability can sign up with the Multistate Tax Commission (MTC), enabling them to become compliant and pay taxes only on future sales.

The states participating are Alabama, Arkansas, Colorado, Connecticut, Kansas, Kentucky, Louisiana, Nebraska, New Jersey, Oklahoma, Texas, Utah and Vermont. The MTC said eight more states are considering participation.

With online sales, merchants are not required to collect sales tax if they don't have a physical presence in a particular state. Amazon complicates matters.

The Fulfillment by Amazon (FBA) program lets sellers pay a fee to use Amazon's warehouses and its massive logistics operation. For businesses that use FBA, their inventory could get shipped to warehouses in certain states, triggering the sales tax requirement.