If you're doing business under something other than your name (or another dba) then you should file the certificate for the new name. Why not just keep it simple and keep everything under one name though? I'd keep one bank account also.
I currently have a DBA "Company X Enterprises" (all names here are fictitious) for which I have an EIN and a bank account (NY state sole proprietorship). All of my business activities use this name and account.
Currently I sell stuff on eBay under 2 different usernames, because the products are totally unrelated. Both of these go to one Paypal account for "Compny X Enterprises."
I would now like to set up a website to sell one of these product lines that is being sold on ebay.
I would like to do business with the name ABCproducts.com for this website. I would like CC payments to go to ABCproducts.com, not "Company X Enterprises". Also I would like the whois info to be registered as ABCProducts.
Is it necessary for me to open another bank account, register a new DBA and have a separate EIN for ABCProducts.com?
Any advice would be greatly appreciated.