Basic net income (loss) per common share is calculated by dividing net income (loss) by the weighted average number of common shares outstanding during the period. Diluted net income (loss) per common share is computed by dividing net income (loss) by the weighted average number of common and dilutive common equivalent shares outstanding during the period. The Company’s potentially dilutive common shares are those that result from dilutive common stock options, non-vested stock relating to restricted stock awards, restricted stock units, deferred stock units and performance shares. Options to purchase shares of common stock as well as unvested restricted stock and performance stock units are considered to be potentially dilutive common shares. However, these shares have been excluded from the calculation of diluted net loss per share as their effect is antidilutive for the six months ended March 31, 2018, as a result of the net loss incurred for the period. Therefore, diluted weighted average number of shares outstanding and diluted net loss per share were the same as basic weighted average number of shares outstanding and net loss per share for the six months ended March 31, 2018.

The calculation of weighted average diluted shares outstanding excludes outstanding stock options associated with the right to purchase 0.2 million shares of common stock for the three and six months ended March 31, 2019 and 2018, respectively, and $0.2 million and 0.2 million shares of common stock in the six months ended March 31, 2019, as their inclusion would have had an antidilutive effect on diluted net income per share for those periods.

The following table sets forth the denominator for the computation of basic and diluted net income (loss) per share (in thousands):

	Three Months Ended				Six Months Ended
	March 31,				March 31,
	2019		2018		2019		2018
Net income (loss) available to common shareholders	$	1,262	$	1,534	$	2,572	$	(22	)
Basic weighted average shares outstanding		13,390		13,102		13,379		13,078
Dilutive effect of outstanding stock options, non-vested restricted stock, restricted stock units, deferred stock units and performance shares		395		363		437		—
Diluted weighted average shares outstanding		13,785		13,465		13,816		13,078

The Company’s Board of Directors has authorized the repurchase of up to $25.3 million of the Company’s outstanding common stock. This authorization does not have an expiration date.