The phrase "an initial deadline of" is correct and usable in written English.
It can be used when specifying the first or preliminary deadline for a task or project.
Example: "We have set an initial deadline of March 15th for the completion of the first phase of the project."
Alternatives: "a preliminary deadline of" or "a first deadline of".
The Fed set an initial deadline of Feb. 22 for the card companies to submit their agreements, and planned to update the site quarterly.
Under Swedish law, the authorities have an initial deadline of noon Monday to authorize his detention or release the man, who is being held on suspicion of attempted hijacking and illegal possession of a handgun.
In related news, the Guardian reports that Facebook has delayed a requirement that UK political advertisers verify their identity — pushing it back from an initial deadline of today to sometime in "the next month", with the company saying it wants to take more time to strengthen the system after a spate of failures.
Timeframes were not adhered to, and despite an initial deadline of 30 June 2010 being set for the phasing out of the legacy qualifications, the process has continually been extended.
Brazil's Public Ministry, a federal regulatory agency, has recommended that Sao Paulo state immediately commence water rationing to avoid a "collapse of reservoirs," but the state government missed an initial deadline on Wednesday to take action.
But nearly a month after an initial deadline for setting the outlines of the deal, the two German automakers sound as though they are no closer than when they started.
The pressure on the accounting firm to resist the looming House subpoena comes after the Treasury Department missed an initial deadline to hand over Trump's tax returns to the House Ways and Means Committee, which then set another deadline of April 23.
Zinovy Pak, the departing supervisor of Russia's chemical weapons destruction program, said Moscow had beaten an initial deadline for dismantling the stock but more problems loomed ahead.
A U.N. Security Council resolution set Nov. 1 as an initial deadline to destroy Syria's ability to produce chemical weapons.
Parties failed to reach a deal before the initial deadline of 16:00 BST on Thursday.
David Cameron promised to force through legislation to extend the deadline to midnight on Thursday after the government's registration website was overwhelmed by a surge in applications in the the final hours before the initial deadline of midnight on Tuesday.
