"extra expenditure" is correct and usable in written English.
You can use it when describing additional costs that weren't originally budgeted for. For example: "The company had to pay for extra expenditure due to unexpected materials costs."
… How much does that extra expenditure matter?
Extra expenditure, particularly on crucial infrastructure, is desperately needed.
Up to £1bn extra expenditure on the vast bureaucracy required by the bill's complexities could be avoided.
But others will automatically turn to their bank for an overdraft to help manage the extra expenditure.
Since there were no resources to meet this extra expenditure, the budget deficit grew, as did the money supply.
The first is that the full impact of the extra expenditure will now only come through in the next parliament.
There is an important tax benefit, too, that often compensates, and more, for the myriad extra expenditures.
This does not include the extra expenditures undertaken by the parent company's other news divisions, including local TV and radio stations.
Drayton McLane Jr., the Astros' owner, had allowed extra expenditures this year to fortify them for a pennant run, but they haven't even been running in place.
The city council protected remaining council services but faced a difficult battle balancing extra expenditures with providing a favourable climate for businesses.
During the two-year stretch when a fractious Democratic majority held the Senate and federal stimulus money filled state coffers, Mr. Silver became virtually unstoppable, driving Gov. David A. Paterson and the Senate to enact billions in extra expenditures and an income tax on the wealthy.
