From the Shutterstock forum for submitters, news about  Withholding Taxes, waiting for the Tax Center launch:

To All Non U.S. Submitters:

We thank you for your patience while we have taken time to carefully design a new Tax Center, in which you will find detailed information on tax matters for non U.S. submitters. We will be launching the Tax Center inside our Submit site soon, and we will send you an email announcement when it has been launched.

We also want to assure you that we will not begin withholding any taxes until after the Tax Center launch, and after you have been given a chance to determine which forms you need to comply and can begin that process. No one should submit any forms to the IRS until we have provided the additional instructions.

We apologize for the delay in providing you more specific instructions but we are using this time to consolidate everything you may need in a single location.

Again, thank you for your patience.

Adam Riggs
President & CFO