Per the Instructions for Schedule K-1 (1120S), page 19:
Codes V through Z. Qualified business income deduction. Generally, you are allowed a deduction of up to 20% of your net qualified business income plus 20% of your qualified REIT dividends and PTP income from your S corporation. The corporation will provide the information you need to figure your deduction.
To enter qualified business income in TaxAct: