Consolidated Statements of Operations - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenue		$ 224,124	$ 150,134	$ 376,307
Operating expenses
Interchange and network fees	[1]	0	0	242,867
Other costs of services		57,706	47,230	44,237
Selling general and administrative		134,872	78,323	62,860
Depreciation and amortization		24,418	18,217	16,564
Change in fair value of contingent consideration		7,140	(1,409)	3,389
Total operating expenses		224,136	142,361	369,917
(Loss) income from operations		(12)	7,773	6,390
Other expenses
Interest expense, net		9,799	8,926	6,004
Other (income) expense		(2,595)	2,621	0
Total other expenses		7,204	11,547	6,004
(Loss) income before income taxes		(7,216)	(3,774)	386
Provision for (benefit from) income taxes		623	(2,795)	(177)
Net (loss) income		(7,839)	(979)	563
Net (loss) income attributable to non-controlling interest		(3,382)	(560)	3,608
Net loss attributable to i3 Verticals, Inc.		$ (4,457)	$ (419)	$ (3,045)
Net loss per share attributable to Class A common stockholders:
Basic (in USD per share)		$ (0.21)	$ (0.03)	$ (0.29)
Diluted (in USD per share)		$ (0.22)	$ (0.03)	$ (0.29)
Weighted average shares of Class A common stock outstanding:
Basic (shares)		20,994,598	14,833,378	10,490,981
Diluted (shares)		31,714,191	27,429,801	10,490,981

[1] Effective October 1, 2019, the Company's revenues are presented net of interchange and network fees in accordance with Accounting Standards Codification Topic 606, Revenue from Contracts with Customers. See Note 2 to our consolidated financial statements for a description of the recently adopted accounting pronouncement.