There is no limit for a person contributing to their own (self) 529 plan.
Actually, there is also no limit for contributing to a 529 where someone else (usually your child) is the beneficiary. The $15,000 limit refers to whether the gift tax return rules apply. There a special rule for 529 plans. Individuals may contribute as much as $75,000 to a 529 plan in 2021 if they treat the contribution as if it were spread over a 5-year period.
