Accounts Receivable-Net

12 Months Ended

Sep. 30, 2012

Accounts Receivable-Net

Accounts Receivable-Net

6. Accounts Receivable—Net

        Net accounts receivable consisted of the following:

	Fiscal Year Ended
	September 30, 2012			September 30, 2011
	(in millions)
Billed	$	1,207.0		$	1,256.3
Unbilled		1,145.1			1,133.6
Contract retentions		156.6			110.5
Total accounts receivable—gross		2,508.7			2,500.4
Allowance for doubtful accounts		(112.8	)		(120.2	)
Total accounts receivable—net	$	2,395.9		$	2,380.2

        Billed accounts receivable represent amounts billed to clients that have yet to be collected. Unbilled accounts receivable represents the contract revenue recognized but not yet billed pursuant to contract terms or accounts billed after the period end. Substantially all unbilled receivables as of September 30, 2012 and 2011 are expected to be billed and collected within twelve months. Contract retentions represent amounts invoiced to clients where payments have been withheld pending the completion of certain milestones, other contractual conditions or upon the completion of the project. These retention agreements vary from project to project and could be outstanding for several months or years.

        Allowances for doubtful accounts have been determined through specific identification of amounts considered to be uncollectible and potential write-offs, plus a non-specific allowance for other amounts for which some potential loss has been determined to be probable based on current and past experience.

        Other than the U.S. government, no single client accounted for more than 10% of the Company's outstanding receivables at September 30, 2012 and 2011.

        The Company sold trade receivables to a financial institution, of which $31.2 million was outstanding as of September 30, 2012. The Company does not retain financial or legal interest in these receivables.