In numerology
What does 999 mean in numerology?
Add every digit
9plus9plus9gives27
Add the digits again
2plus7gives9
Three nines add to 27, and 27 reduces back to 9.
It is the only number in this set that returns to itself, which makes it unusually clean symbolism: an ending that resolves into an ending, with nothing left over. Nine is already the digit of the long view and of letting go, so 999 has no counterweight and no second theme. Everything about it points at closing rather than at whatever comes afterwards.

