There are a lot of moving parts to this question.
First, you need to determine in which states you have "nexus" and then determine do those states require you to charge sales tax, as each state has different rules.
As an example, MA requires salesforce.com to charge sales tax to MA customers but does not require newyorktimes.com to charge sales tax. The difference is that users can manipulate data on salesforce.com vs. neworktimes.com is read only. This example can only be applied to MA, Arizona, Illinois, New York, Texas, Pennsylvania and Washington State (as of now).
There are also "click-through" and "affiliate" nexus rules that need to be considered.
Be careful, as state and local taxation has become a very hot due diligence issue in M&A transactions. So, if you plan to sell your business in the next few years, you want to get this right. Also, the Officers and Directors are personally responsible for uncollected Sales tax.
You are best to get an expert to review your sales tax compliance, as it is a very specialized area and changing constantly. I am not an expert, but know of some firms that offer this service at a very reasonable rate.
Feel free to call me.
Accountalent Management Corp.
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Cambridge, MA 02139
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