I could go into prepayment rules, etc, which suggest that it's...

I could go into prepayment rules, etc, which suggest that it's pretty tricky to try to argue that. If you got audited by the ATO, then you'd probably lose. But your point is reasonable, so I'll avoid the technicals, and answer in good faith:

I've seen individuals do it. Prepay a bunch of costs and claim it. Most get away with it. Depending on what it is, you can usually have a reasonable position.
Small businesses - mixed results. Yeah, i've seen some try to prepay rent and things like that, and if the accountant isn't paying attention, they'd probably get away with it. Technically, if there's financial statements, and you prepay something over $1000, it should be taken out of the expenses and put in as a prepayment asset until it is used. If your accountant doesn't care, and the ATO don't select you for audit, you'd get away with it, but it is technically wrong.
Audited businesses - no. The second you're doing general purpose financial reports, auditors actually insist that you keep to financial reporting standards. And this is not a complicated one. It's not allowed, every corporate accountant knows the rules and adjusts for prepayments at month end. At financial year end, you go through it with a fine tooth comb and make sure you haven't missed any... it's really cut and dry.