The phrase "an additional concession" is correct and usable in written English.
You can use it when referring to an extra allowance or compromise made in a negotiation or agreement.
Example: "After much discussion, the management agreed to an additional concession to meet the employees' demands."
Alternatives: "a further concession" or "an extra concession".
The union, however, may find it difficult to make any additional concessions.
The specifics were the same as those proposed by Mr. Obama in his budget earlier this year, without any additional concessions.
But Mr. Reid's bill is hardly a terrible outcome for them, and they will probably win at least a few additional concessions out of Democrats over the weekend.
The Garden will also have 58 more suites, a larger concourse on the eighth floor and additional concession stands and bathrooms.
The wages for the new hires, however, are $10 to $15 an hour less than the pay scale for hourly employees already on staff — with the additional concession that the newcomers will not catch up for the foreseeable future.
A second level would include space for additional concessions and a VIP Club.
In effect, diplomats say, Lebanon and Syria see the Israeli commitment to withdraw as a chance to exact additional concessions from Israel on other long-running issues.
What they got was continued animosity from Palestinians, pressure for additional concessions, a near doubling of the rate at which Israeli Arabs murdered Israeli Jews, and a rising challenge to their sovereignty in Jerusalem.
Ultimately, they said, the agency's chairman, Robert Pitofsky, decided to accept a proposed settlement because of additional concessions that the companies had made in the last month.
But the bank and its peers still face demands from state attorneys general to make additional concessions, including a multibillion-dollar settlement.
