You'll keep the majority after federal withholding and final taxes, typically 60-75% of the prize depending on your income bracket, since South Dakota has no state tax. Initial federal withholding of 24% applies to prizes over $5,000, and additional taxes may be due based on your total income. No local or state taxes reduce your take-home further. For example, with a $500,000 lump-sum win, $120,000 is withheld federally upfront, giving you $380,000 immediately. After filing, if you're in the 32% bracket, you might owe another $40,000, netting about $340,000 total. Consult a tax professional to estimate your net based on deductions and credits.