14. Trade accounts receivable

As of December 31, trade accounts receivable were as follows:

in million €	2009	2008
Trade accounts receivable	2,794	2,734
less allowance for doubtful accounts	285	257
Trade accounts receivable, net	2,509	2,477

All trade accounts receivable are due within one year.

The following table shows the development of the allowance for doubtful accounts during the fiscal year:

in million €	2009	2008
Allowance for doubtful accounts at the beginning of the year	257	223
Change in valuation allowances as recorded in the consolidated statement of income	174	159
Write-offs and recoveries of amounts previously written-off	- 141	- 129
Foreign currency translation	- 5	4
Allowance for doubtful accounts at the end of the year	285	257

The following table shows the ageing analysis of trade accounts receivable and their allowance for doubtful accounts:

in million €	not overdue	up to 3 months overdue	3 to 6 months overdue	6 to 12 months overdue	more than 12 months overdue	Total
Trade accounts receivable	1,648	450	225	187	284	2,794
less allowance for doubtful accounts	7	32	27	45	174	285
Trade accounts receivable, net	1,641	418	198	142	110	2,509