Wise Investment in Children Act of 2021 or the WIC Act of 20 21 This bill expands eligibility for children to receive benefits under the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). Specifically, the bill extends eligibility for the program until the period that ends on the earlier of the sixth birthday of a child or when the child enters kindergarten; extends the certification period under the program for infants to up to two years, instead of the current one year; and increases the certification time under the program for postpartum women to a period of up to two years. The bill also authorizes the Department of Agriculture to grant a waiver to a state, on request, that waives certification deadline requirements for the eligibility extensions if such state demonstrates there are unusual technological barriers to implementation, operational costs are not affordable within the nutrition services and administration grant of the state, or it is in the best interest of the program.