I was invited for a conference/meeting to the US for graduate students organized by an US cooperation. Our costs were supposed to be reimbursed by the cooperation in a form of a stipend. After the event, I was sent an 8BEN IRS form, which I am supposed to send the company to receive my reimbursement. I was not aware that I would need to file any tax report to the IRS and mistakenly travelled using the ESTA tourist VWP.
Is it possible to file this stipend legally on the ESTAT VWP? If so how do I declare the reimbursement correctly?