A grandparent wants to contribute to a grandchild's 529 plan. Under the special gift tax provision, the grandparent can contribute up to how many years' worth of annual gift tax exclusions at once?

Why B — 5 years

529 plans offer a unique 5-year gift tax averaging provision. A contributor can front-load up to 5 years' worth of annual gift tax exclusions in a single year without incurring gift tax (e.g., 5 x $18,000 = $90,000 in 2024). The contribution is treated as if made over 5 years for gift tax purposes. If the contributor dies within the 5 years, a prorated portion is included in their estate.