Keep billing and payment work easy to follow

Paying contractors in their own currencies out of your own bank accounts means one account per currency, and every one of them has to hold money before a run starts. The buffer gets sized once, against the biggest run anyone can remember, and then nobody looks at it again. What that costs is cash you cannot spend, parked in a currency you may not need again this quarter. Topping an account up is itself a cross-border payment with its own value date, and euro settlement in T2, the system the euro area central banks operate, does not run on Good Friday, Easter Monday, 1 May or 26 December. None of those four is a Federal Reserve holiday, so a US payment calendar does not show them.

Volume is rarely what forces this decision. A team can push a great many payments through one bank and one accounting system without any of it being hard, because every question has an answer in one of two places. What changes the arithmetic is how many parties hold part of the answer: a second bank, a provider whose statuses stop inside its own portal, a marketplace that decides what a seller is owed, a tax authority that takes its cut before the money reaches you. Each of those adds a place to look. The cost of joining them up is that somebody has to make the identifiers agree first, and agreeing what a customer reference means across four systems is a conversation between teams that happens before anything is built.

Some countries require a customer to deduct tax from what they pay a foreign supplier, and the reduced rate a treaty allows depends on proving where the supplier is resident. For a US company that proof is Form 6166, a letter the IRS issues confirming US residence for a tax year. It is requested on Form 8802, costs $185 for a non-individual applicant, and the IRS asks you to allow at least 45 days. Nobody starts that clock at contract signature. The first invoice goes out while the request is still queued, the customer deducts at the domestic rate because their law tells them to, and the invoice sits open against a payment that is correct. Recovering the difference means a refund claim in the customer's country, which asks for the same certificate.