"twice annually" is correct and usable in written English.
It is used to express that something happens two times each year. For example: We review our budget twice annually to ensure we are staying on track.
Major grants are issued twice annually.
The seminar has happened twice annually since 2003.
The Center's Board meets twice annually for a two-day retreat in Monterey, California.
Meetings of heads of state are usually scheduled annually; meetings of foreign secretaries, twice annually.
Waterfowl are abundant, and migratory Canadian geese by the thousands visit refuges twice annually.
It added: "To maintain momentum, we have agreed to meet twice annually to review progress in the working group.
Federal regulations require that the public should have been alerted twice annually about planned changes in the works.
Intestinal worms affect one in four people worldwide, but can be controlled by taking medicine twice annually.
For over a decade, I got to return to Cornell twice annually recruiting new staff for my firm.
1. Timing of Decisions Ivy League institutions mail admission decision letters twice annually, in mid December and late March.
The Council, consisting of 40 members, meets twice annually and is responsible for governing the organization between Assembly sessions.
