What is onus payment?

Could you please clarify what you mean by "onus payment"? It's not a commonly used term in the world of finance or cryptocurrency. Are you referring to a specific type of payment obligation, such as a penalty or fee that is incurred when certain conditions are not met? Or perhaps you're referring to the responsibility or burden of payment that one party bears in a financial transaction? Without more context, it's difficult to provide an accurate description of "onus payment." Can you provide any additional information or clarify your question?