The phrase "additional duty" is correct and usable in written English.
It can be used when referring to an extra responsibility or task that is assigned in addition to existing duties.
Example: "As part of my role, I have taken on an additional duty of training new employees."
Alternatives: "extra responsibility" or "supplementary task".
This would mean – where an order has been granted – that these venues will have an additional duty to stop guys using poppers.
Treasury figures show the chancellor has calculated that additional duty will add £400m to his purse by April 2009, and a further £1.13bn in the subsequent two years.
For example, it gave a 5% additional duty credit and carved out separate allocations under existing market-promotion funds for the export of toys and sports goods.
Responding to the complaints was an additional duty for these employees, who also handled external correspondence for the agency, the report said.
He argued that the federal government had an additional duty to take aggressive steps "to prevent the starvation or the dire want of any of its fellow men and women who try to maintain themselves but cannot".
Moreover, given the ad hoc nature of the teams — F.E.T. members have "day jobs," serving as logisticians or intelligence officers or in other vital positions — their commanders are often understandably reticent to give up an individual for an additional duty.
The additional duties make Mr. Thursfield a busy man.
Each of India's 28 states levies additional duties.
Mr. Vein himself has taken on additional duties that a chief financial officer would normally perform.
WEST VIRGINIA--Named Bill Stewart receivers coach; offensive line coach Bill Legg was given the additional duties of offensive coordinator; assistant head coach Doc Holliday was given the additional duties of quarterbacks coach.
The European Union is threatening to retaliate by imposing additional duties on imports from the United States worth about $300 million a year.
