My company, tremendous.com, does this, including the tax form collection process if spend exceeds $600 / person. Our primary use case is user research incentives, but interview incentives is an analogous problem.
Basically no strings attached for both sides. We do complete a compliance review for businesses signing up for our site (given we're a payments company), but it's basically invisible at smaller volumes.
Basically no strings attached for both sides. We do complete a compliance review for businesses signing up for our site (given we're a payments company), but it's basically invisible at smaller volumes.