Allowance for Doubtful Accounts Receivable and Sales Returns

12 Months Ended

Dec. 31, 2020

Receivables [Abstract]

Allowance for Doubtful Accounts Receivable and Sales Returns

Note 6. Allowance for Doubtful Accounts Receivable and Sales Returns

Activity in the allowance for doubtful accounts receivable (in thousands):

	Years ended December 31,
	2020		2019
Balance, beginning of year	$	484	$	475
Addition to allowance	117		24
Amounts written off	(30)		—
Effects of foreign currency translation	27		(15)
Balance, end of year	$	598	$	484

Activity in the allowance for sales returns (in thousands):

	Years ended December 31,
	2020		2019
Balance, beginning of year	$	32	$	85
Addition (reduction) to allowance	(1)		(32)
Amounts written off	—		(21)
Balance, end of year	$	31	$	32
Total, Allowance for Doubtful Accounts Receivable and Sales Returns	$	629	$	516

Two customers individually comprised more than 10% of trade accounts receivable at December 31, 2020, with the customers accounting for 19% and 10% each. Two customers individually comprised more than 10% of trade accounts receivable at December 31, 2019, with the customers accounting for 26% and 11% each.

Two customers accounted for 25%, or $17.3 million, of consolidated revenue during the year ended December 31, 2020, in the Mobile Services segment.

One customer accounted for 13%, or $8.8 million, of consolidated revenue during the year ended December 31, 2019, in our Mobile Services segment.