SWIFT ISO 15022 - Code TREATBENF Financial acronyms The entire acronym collection of this site is now also available offline with this new app for iPhone and iPad. Meaning Claim of Tax Treaty Benefits Usages Message type Field number Tag MT574.W8BENO (IRS 1441 NRA-Form W8-BEN) 20 16R (Start of Block) MT574.W8BENO (IRS 1441 NRA-Form W8-BEN) 24 16S (End of Block)