Annual report pursuant to Section 13 and 15(d)

Cover

v3.21.4
Cover - USD ($)
 9 Months Ended
Sep. 30, 2021
Dec. 16, 2021
Mar. 31, 2021
Cover [Abstract]      
Document Type 10-K/A    
Amendment Flag false    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Sep. 30, 2021    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2021    
Current Fiscal Year End Date --09-30    
Entity File Number 000-54986    
Entity Registrant Name ARCH THERAPEUTICS, INC.    
Entity Central Index Key 0001537561    
Entity Tax Identification Number 46-0524102    
Entity Incorporation, State or Country Code NV    
Entity Address, Address Line One 235 Walnut Street    
Entity Address, Address Line Two Suite 6    
Entity Address, City or Town Framingham    
Entity Address, State or Province MA    
Entity Address, Postal Zip Code 01702    
City Area Code 617    
Local Phone Number 431-2313    
Title of 12(g) Security Common Stock, par value $0.001 per share    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Public Float     $ 32,000,000
Entity Common Stock, Shares Outstanding   237,169,770