Tom-Next Rolls and Overnight FX Financing

Standard FX trades settle two business days after the trade date — spot. But a trading desk that wants to hold a currency position open indefinitely, without ever actually taking delivery of the underlying currency, has to roll that settlement forward one day at a time, every single day, for as long as the position stays open. The mechanism for doing that overnight is the tom-next (tomorrow-next) swap, and the price of it is a live, daily readout of overnight funding conditions in both currencies.

Rolling a position without ever settling it

Suppose a desk buys dollars against yen spot, intending to hold the position for weeks. Left alone, that trade would settle in two days and the desk would own actual dollars sitting in an account, funded by actual yen it borrowed to pay for them. Instead, the desk executes a tom-next swap: it sells dollars for value tomorrow and simultaneously buys them back for value the day after (next). Do this every trading day and the position's settlement is perpetually pushed one day further out, never actually landing.

Worked example

A desk is long $50 million against short yen, and tonight's tom-next points for USD/JPY are quoted at -0.8 pips (dollars rolling at a discount, meaning dollar overnight rates sit above yen overnight rates that night).

1. Convert points to a rate. With spot at 150.00, the points represent $-0.008 / 150.00 = -0.0000533$, or about -0.00533% overnight.
2. Annualize. Multiply by 365: $-0.00533\% \times 365 \approx -1.95\%$ — roughly the overnight USD-JPY rate gap the swap market is pricing that specific night.
3. Cash effect. On $50 million, one night's roll costs approximately 50{,}000{,}000 \times 0.0000533 = \2{,}665$ — a small daily debit that, compounded over weeks, adds up to a real financing cost on the position, separate from any move in the exchange rate itself.

What this means in practice

Because tom-next is priced fresh every single trading day, it reacts to overnight funding stress faster than almost any other FX-adjacent number: a spike in tom-next points around a quarter-end, when banks shrink balance sheets to manage regulatory ratios, or during a funding squeeze in one currency, shows up as an outsized, temporary cost to roll a position that has nothing to do with the currency pair's spot direction. Desks running large overnight FX books watch tom-next pricing as an early signal of dollar (or any currency's) funding stress, often before it's visible anywhere else.