The BP number is used as an identification number for businesses whilst taxpayers can use the assessment number to identify their tax arrears before making payments. Think of it as an invoice of sorts.
For the Assessment number you'll fill out similar details apart but your status (business/individual) is not required.
ZIMRA's Commissioner-General Faith Mazani believes partnering with OneMoney will afford the ordinary person who hasn't paid taxes because they don't know how to an opportunity to finally pay their taxes:
"I'm speaking here about the ordinary honest citizen who does not own up, not because of a lack willpower, but a lack of know-how. People discover that they owe an obligation to ZIMRA at the point where we come to collect, whilst, in other cases, the knowledge was available but a convenient method of meeting the obligation was not, until now." Faith Mazani - ZIMRA Commissioner-General
From OneMoney's perspective, this partnership will be one of the ways they hope to acquire customers by offering a service that isn't offered by market leader EcoCash.
Whilst that is a good way for NetOne to differentiate OneMoney it was interesting to hear the ZIMRA commissioner-general mention that ZIMRA was proud to collaborate with a fellow state-owned enterprise:
"We as ZIMRA, are especially proud of this collaboration as both NetOne and ourselves are part of the same family of State-Owned Enterprises." Faith Mazani
I'm not sure if this means that ZIMRA's partnership with OneMoney could remain exclusive because of their special relationship.