on sold list click "send payment details" you can add message then send invoice
on day 3 send invoice, with note saying please pay by thursday 6pm as i need to wrap to post friday morning
I sell as business so I don't rush to open cases
on day3/4 i send invoice
on day 6 email saying I am sure it is an oversight but it has been 6 days ince you won auction, please pay by (x normally another 48 hours) if a problem please get in touch, some are waiting to bid on other items for combined postage but never said... i can't mind read!
day 7/8 open case
I would say 50% pay within 24 hours another 35% within the 4 days allowed by ebay
most on receipt of email,
have opened 38 non payment cases about 15 then paid so 22 have non payment strikes ( out of about 1000 sales)
however as private seller I may just send invoice day 3/4 and open case day 5/6
you always need to send invoice if combining postage for more than 1 item