Please be advised that the Sprintax calculations are based on the IRS/state requirements and tax tables.
If you owe money the reason may be because there were underpaid taxes, not enough tax was withheld from your income. That is a very common case with nonresidents. The reasons may vary and the best thing to do is check if you have uploaded your payment document using our OCR technology, and you noticed that something has not transferred over. If that is the case, please try uploading a clearer picture of your document, or manually fill in any information that did not transfer over.
If everything is indeed correct, in order to have clear records and no issues with future visa applications, it is best to pay the liability by the deadline of 15th of April (if you live in Massachusetts or Maine, you have until April 17th, 2024. That is because of the Patriots' Day holiday in those states), otherwise you may be penalized.
If you wish to pay online, you can do it here - https://www.irs.gov/payments (for your federal liability only. For the state liabilities, you will have an exact site provided on the final generated State tax return).