Is Sep 30th the hard cut-off for submitting documents for pay? Can I get paid for Sep FY 22 CCC if it is submitted on 1st Oct 23?

You'll still get paid. You did the travel, you have to be reimbursed. It's just a huge pain because the money is allocated by FY. So someone will probably have to go back in and allocate money to last year's funds, which causes extra work, usually a memo by someone important, or other hurdles to jump through.

Learning point for you, the Army tries to stop all spending and obligation funds at the end of the FY and close out any vouchers, so they can close out the fiscal year. Most commands will turn off GPC cards mid September and stop any unnecessary purchases as well. Any travel that goes through the end of the FY and in to the next FY is a whole special level of hell in Dantes Inferno.

1LT (Join to see), you're asking a local policy question vs a hard and fast rule by regulation/law, however those policies will cause you no end of trouble.

To your specific question - No, there is no hard cut-off for the documents by regulation/law, but there may be one by policy. Your best bet is to talk to the full-time AGR staff at your unit ASAP and explain the situation - you have the paperwork, it's all correct but is just lacking a signature.

In some cases, the commander may sign it or have signature authority delegated to his full-timers (many commanders do). Additionally, the "hard cut-off" date for you might not be the cut-off date for the unit (they will usually back it up a few days in order to get the stuff done they need to do before sending it to higher).

Again, bottom line - talk to your unit full-timers ASAP.

You will be paid. It is illegal to make a person work for the government and not pay them. This philosophy has been adopted to prevent the government from abusing government employees.