4. Trade Accounts and Financing Receivables

Trade accounts receivable are reflected in the following table (in thousands):

	June 30, 2018			September 30, 2017
Trade accounts receivable	$	14,719		$	10,830
Allowance for doubtful accounts		(3,569	)		(1,395	)
	$	11,150		$	9,435

The allowance for doubtful accounts represents the Company’s best estimate of probable credit losses. The Company determines the allowance based upon historical experience and a current review of its balances. Accounts receivable balances are charged off against the allowance whenever it is probable that the receivable will not be recoverable. During the three months ended June 30, 2018, the Company recorded bad debt expense of $2.7 million primarily attributable to a trade accounts receivable from a customer which filed for bankruptcy protection during the period. While the Company is uncertain of the ultimate amount of bad debt that will result from the bankruptcy proceedings, it has provided a bad debt allowance for all of its pre-petition bankruptcy receivable claims. Should any portion of these pre-petition claims be recovered in the future, the Company will reverse such bad debt expenses.

Financing receivables are reflected in the following table (in thousands):

	June 30, 2018			September 30, 2017
Promissory notes	$	6,661		$	4,306
Sales-type lease		6,127			8,581
Total financing receivables		12,788			12,887
Unearned income from promissory notes		(95	)		(90	)
Unearned income from sales-type lease		(300	)		(527	)
Total unearned income		(395	)		(617	)
Total financing receivables, net of unearned income		12,393			12,270
Less allowance for doubtful promissory notes		(1,849	)		(1,020	)
Less current portion of financing receivables		(5,031	)		(3,055	)
Non-current financing receivables	$	5,513		$	8,195

During the nine months ended June 30, 2018, the Company issued promissory notes to customers totaling $4.0 million in connection with the sale of rental equipment. Cash flows from financing receivables related to the sale of rental equipment for the nine months ended June 30, 2018 of $3.6 million are included in proceeds from the sale of used rental equipment in the consolidated statements of cash flows.