Hebrews 9:7

But into the second, only the high-priest once a year, not without blood, which he offereth for himself and the errors of the people:

Hebrews 9:25

Nor did he enter, that he might offer himself often (as the high-priest entered into the holy place every year with the blood of others.)

Hebrews 10:3

But in those sacrifices, there is a commemoration of sins every year.

Hebrews 10:14

For by one offering he hath perfected for ever them that are sanctified.

Treasury of Scripture Knowledge

Summary

And this shall be an everlasting statute unto you, to make an atonement for the children of Israel for all their sins once a year. And he did as the LORD commanded Moses.

Bible References

Once a year

Hebrews 9:7
But into the second, only the high-priest once a year, not without blood, which he offereth for himself and the errors of the people:
Hebrews 10:3
But in those sacrifices, there is a commemoration of sins every year.