Consolidated Statements of Operations - USD ($)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Revenues
Revenues from contracts with customers	$ 223,959,000	$ 207,884,000
Net dealer inventory (losses) gains	1,076,000	(1,466,000)
Interest and dividends	4,334,000	5,822,000
Other	506,000	701,000
Total Revenues	229,875,000	212,941,000
Operating Expenses
Commissions, compensation and fees	195,938,000	175,453,000
Clearing fees	8,474,000	4,808,000
Communications	3,588,000	2,816,000
Occupancy	5,053,000	4,301,000
Licenses and registration	3,871,000	2,960,000
Professional fees	9,320,000	7,306,000
Interest	90,000	32,000
Depreciation and amortization	2,854,000	1,832,000
Other administrative expenses	9,203,000	11,333,000
Total Operating Expenses	238,391,000	210,841,000
Income before Other Income (Expense) and Income Taxes	(8,516,000)	2,100,000
Other Income (Expense)
Gain on disposal of Gilman branches	297,000
Change in fair value of warrants	140,000
Other income		60,000
Total Other Income (Expense)	437,000	60,000
Income (Loss) before Income Taxes	(8,079,000)	2,160,000
Income tax expense (benefit)	(1,865,000)	319,000
Net Income (Loss)	(6,214,000)	1,841,000
Net income (loss) attributable to non-controlling interest	276,000	(2,660,000)
Net income (loss) attributable to National Holdings Corporation common shareholders	$ (5,938,000)	$ (819,000)
Net income (loss) per share attributable to National Holdings Corporation common shareholders - Basic (in dollars per share)	$ (0.44)	$ (0.06)
Net income (loss) per share attributable to National Holdings Corporation common shareholders - Diluted (in dollars per share)	$ (0.44)	$ (0.06)
Weighted average number of shares outstanding - Basic (in shares)	13,414,009	12,821,581
Weighted average number of shares outstanding - Diluted (in shares)	13,414,009	12,821,581
Commissions [Member]
Revenues
Revenues from contracts with customers	$ 116,898,000	$ 86,929,000
Banking [Member]
Revenues
Revenues from contracts with customers	51,280,000	69,656,000
Investment Advice [Member]
Revenues
Revenues from contracts with customers	35,676,000	34,400,000
Clearing Service [Member]
Revenues
Revenues from contracts with customers	9,957,000	8,092,000
Tax Preparation and Accounting [Member]
Revenues
Revenues from contracts with customers	$ 10,148,000	$ 8,807,000