TRADE ACCOUNTS RECEIVABLE, NET OF ALLOWANCES

12 Months Ended

Dec. 31, 2012

TRADE ACCOUNTS RECEIVABLE, NET OF ALLOWANCES

6. TRADE ACCOUNTS RECEIVABLE, NET OF ALLOWANCES

Unbilled trade accounts receivable relate to services earned under time and material arrangements, maintenance and license arrangements that had not been invoiced as of December 31, 2012 and December 31, 2011, respectively.

(in thousands)	December 31, 2012			December 31, 2011
Trade accounts receivable	$	112,106		$	77,123
Unbilled accounts receivable		22,923			22,096
Total accounts receivable		135,029			99,219
Allowance for doubtful accounts		—			(31	)
Allowance for sales credit memos		(963	)		(895	)
Total allowance		(963	)		(926	)
	$	134,066		$	98,293

The Company records an allowance for estimates of potential sales credit memos when the related revenue is recorded and reviews this allowance periodically. The following reflects the activity of the allowance for sales credit memos for each of three years ended December 31:

(in thousands)	2012			2011			2010
Balance at beginning of year	$	895		$	1,027		$	540
Provision for credit memos		1,773			2,877			3,050
Credit memos issued		(1,705	)		(3,009	)		(2,563	)
	$	963		$	895		$	1,027