Anything over 5k you pay both federal and state taxes. So if you win 50k the CT lottery will deduct roughly 30% and you end up with a check for 35k.

The CT Lottery is required by law to report and withhold federal income tax (currently 24%) on all gambling winnings valued at more than $5,000. (Under certain circumstances this tax rate may be 30%.) In addition, the Lottery is required to report to the IRS gambling winnings that are $600 or more, and at least 300 times the amount of the wager. 

CT Lottery Federal Tax ID Number: 06-1457386

State Income Tax: 6.99% The CT Lottery is required by law to withhold Connecticut state income tax (currently 6.99%) on all gambling winnings that are either: 1) subject to federal withholding tax (i.e. proceeds more than $5,000); or 2) reportable for federal tax purposes (i.e. $600 or more and at least 300 times the amount of the wager.) Connecticut state income tax is required on all CT Lottery winnings regardless of state residency.