scall said:
30 days is the standard.
On invoices, always state this. After 30 days send a reminder with 7 days payment window. After that I'd send a final reminder with a polite threat of "further action".
After that threaten with small claims court and charge interest. There's a great template out there which references various Acts
Pretty much this, although I had some customers here a couple of years ago that started off with on time payments, then started delaying. Obviously they were doing this with other suppliers until eventually they closed shop and literally fucked off. I'm lucky the amounts were not that large, but it makes you think 'who the fuck can you trust'.