5 years from senior year, one can contribute large amount

https://www.investopedia.com/articles/personal-finance/010616/529-plan-contribution-limits-2016.asp#:~:text=State%2DSpecific%20529%20Contribution%20Limits,-All%20states%20have&text=On%20the%20high%20end%2C%20states,have%20maximum%20limits%20of%20%24500%2C000.

 

Gift Tax Considerations

Usually, annual contributions to any individual above a certain threshold ($17,000 in 2023, up from $16,000 in 2022) would count against your lifetime gift tax exemption of $12.92 million for singles and $25.84 million for married couples. This is an increase from 2022's $12.06 million and $24.12 million.1213

 

However, there is an exception made for contributions within a 529 plan. You can give five years' worth of contributions in a one-time lump sum. For example, a grandparent can give an $85,000 one-time lump-sum contribution to a 529 plan ($17,000 per year multiplied by five years) with the understanding that it would cover five years’ worth of gifts. As long as that person doesn’t contribute again in the next five years, there are no tax consequences.14