Hello, I filed my taxes but UPS doesn't know if they delivered the package. I can't find it on the IRS website and its been 4 weeks. What should I do?

Why doesn't UPS know? it's not the USPS.  Are you due a refund?  If so there no penalty if you have to refile after 7/15. Keep checking your refund status.  if the IRS got your return, the delay is not unexpected since the IRS was not processing paper returns for about 2 months. Your return will be processed in the order received. it's always advisable that when you send important documents you get proof of delivery.   if you owe, and can't get info by 7/15 you'll have to choose whether or not to resubmit.  there could be late payment and filing penalties if the IRS did not receive the return and you can't prove to the satisfaction of the IRS that you filed before the due date using UPS.  if you do decide to refile, I would use USPS and get proof of delivery.