People who ask a question like this are generally the target of a contest scam. There is no such thing as a National Prize Authority in the US. The closest I can come to that is the National Prize Reporting Center, which doesn't really exist, and to which the Better Business Bureau has given an F rating and a red fraud alert.
The very fact that you have asked this question means that this is a scam. You must always enter a contest to win it, and if you don't recognize this name, then it's clear that you never entered any contest it supposedly sponsors.
Scammers always want you to believe that you can be picked out of thin air and become a contest winner. You can't. You must always enter a contest to win it.
Lottery winners are paid out of the proceeds of lottery tickets. If you don't buy your ticket you can't win, and you must present a valid ticket to claim your winnings. US lottery tickets cannot be sold on line. It's against Federal law. You must buy them in person from agents at specially designated locations.
Sweepstakes winners must complete an entry form and sign up for the contest. Sweepstakes also require you to submit your half of the entry form as proof before you can claim your prize. Your half of the form matches the information the company has on the other half.
Finally, when you win a real contest, the money already belongs to you. So you NEVER have to pay anything up front to receive something that's already yours.
In any legitimate contest, if there were indeed any transfer expenses, the contest would simply deduct it from your money which they already have and just give you a check for the rest. But with a scam contest, if you notify them, they will ask for money up front for taxes, insurance, courier or transfer fees, or they will give you a partial check and ask you to deposit it and use the money to pay a third party. There's no need for any of that with a real contest.
The up front fee is the #1 sign of a contest scam.
I hope you haven't sent off any money to these thieves or deposited a check. If you have paid these folks anything, however, consider it gone and consider yourself the victim of a crime. If you can find out who these people really are and where, you can sue them or seek to have them prosecuted, but finding them will be a job for law enforcement or a private investigator.
Since they claim to be a US contest, report them to the FBI online at their Internet Crime Complaint Center at IC3.gov, whether you've sent them money or not .