The question is not currency but whom you are paying for what, and which forms are involved.
Are you paying U.S. vendors that operate in Canada? Then you want a W-9 and must report on a 1099-MISC.
Are you paying Canadian vendors (who may have U.S. TINs) operating in the U.S.? You’ll need, depending on the vendor, a W-8BEN-E and to report on 1042-S – no withholding if they claim exemption under the tax treaty with Canada on the W-8; or a W-8BEN for an individual; or an 8233 for an individual providing personal services.
Are you making non-FATCA payments, e.g., payments for services, to Canadian vendors who are performing the services in Canada? Then you do not have to report the payment.
Are you paying for merchandise only? No reporting, whether U.S. or Canadian.
So there are many questions here. We recommend you see several of the articles under the Network’s 1042-S reporting section.