3.ACCOUNTS RECEIVABLE

Accounts receivable are recorded at the invoiced amount and do not bear interest. The allowance for doubtful accounts represents our best estimate of the amount of probable credit losses in the existing accounts receivable balance, and we review the adequacy of the allowance for doubtful accounts on a regular basis. We determine the allowance for doubtful accounts using historical write-off experience based on the age of the receivable balances and current general economic conditions. Receivable balances past due over 90 days, which exceed a specified dollar amount, are reviewed individually for collectability. As we increase sales to governmental organizations, including school districts, and offer longer payment terms on certain contracts (which are still within our normal payment terms), our collection cycle may increase in future periods. If the risk of non-collection increases for such receivable balances, there may be additional charges to expense to increase the allowance for doubtful accounts.

Account balances are charged off against the allowance after all means of collection have been exhausted and the potential for recovery is considered remote. We do not have any off-balance sheet credit exposure related to our customers nor do we generally require collateral or other security agreements from our customers. Activity in our allowance for doubtful accounts was comprised of the following for the periods indicated (in thousands):



YEAR ENDED
AUGUST 31,		2018		2017		2016
Beginning balance	$	2,310	$	1,579	$	1,333
Charged to costs and expenses		2,029		1,747		2,022
Deductions		(784)		(1,016)		(1,776)
Ending balance	$	3,555	$	2,310	$	1,579

Deductions on the foregoing table represent the write-off of amounts deemed uncollectible during the fiscal year presented. Recoveries of amounts previously written off were insignificant for the periods presented.