The battle over sales-tax fairness is gaining steam, with bipartisan bills mandating Internet companies to collect sales tax recently introduced in the House and the Senate.The two bills differ in certain respects, but both provide two options for states to collect sales tax from consumers who purchase goods on the Internet.States that voluntarily join the Streamlined Sales and Use Tax Agreement can require remote sellers to collect and remit sales and use taxes after 90 days. Twenty-four states have currently joined this agreement.States that do not wish to become members of SSUTA could collect the taxes only if they adopt certain minimum simplification requirements.Both bills include a "small-seller exemption," which exempts retailers whose sales fall below a certain threshold ($500,000 in-state a year in the Senate version, and less than $100,000 in-state or $1 million nationally in t