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Note 9 - Income Taxes - Reconciliation of Income Tax Expense (Details) - USD ($)	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Income before income taxes	$ 17,371,505	$ 15,457,507
Corporate federal income tax rate	21.00%	21.00%
Income tax expense computed at the federal statutory rate	$ 3,648,016	$ 3,246,076
State income taxes, net of federal income tax expense	853,582	763,518
Net amortization of excess deferred taxes on regulated operations	(366,844)	(315,708)
Net amortization of RNG tax credits	(100,649)	(100,649)
Reserve for unrecognized tax benefits	0	82,000
Other, net	57,430	21,374
Total income tax expense	$ 4,091,535	$ 3,696,611

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