Cross-broker swap arbitrage, swap-free account strategies, the net-APR math, and why brokers work hard to shut it down.
Swap arbitrage is a strategy that profits from differences in overnight swap (rollover) rates rather than from price movement. You hold a position that earns a positive swap and an offsetting position that pays little or no swap, so the direction is hedged and the net rollover is the return. It comes in two main forms: across two brokers with different swap rates, or between a normal account and a swap-free account. The idea is simple, but the edge lives entirely in the fine print: broker markups, swap-free admin fees, and terms of service are all designed to close it.
A swap, also called rollover, is the interest you pay or earn for holding a forex position overnight. It exists because every currency pair is really two currencies with different interest rates, and holding the pair overnight means financing one with the other.
The basic rule: if you are long the currency with the higher interest rate, you tend to earn a positive swap; if you are short it, you tend to pay a negative swap. Two practical details make this messier than the textbook version:
| Detail | What it means in practice |
|---|---|
| Broker markup | Brokers add a spread to raw swap rates, so both the long and the short side are often net negative |
| Triple swap day | To account for weekend settlement, most venues charge or credit three times the usual swap on one midweek day (commonly Wednesday) |
| Rate changes | Swap rates move with central-bank rates and broker policy, so a gap that exists today can vanish next week |
Swap arbitrage builds a position where the swap you earn on one side is larger than the swap you pay on the other, while the two sides cancel out the price risk. Because the currency exposure is offset, you are not betting on the exchange rate. You are harvesting the rollover gap between two places that price it differently.
This is where it differs sharply from the carry trade, which people often confuse it with.
Carry tradeBuy a high-interest currency and hold it, earning the swap but taking the full directional risk of the exchange rate. If the pair moves against you, the price loss can dwarf the swap earned. It is a directional bet with a yield. |
Swap arbitrageHold the positive-swap exposure and an offsetting position that neutralizes the direction, so you keep the swap gap without the exchange-rate risk. It is an arbitrage on the rollover itself, not a bet on price. |
You open the same pair in opposite directions at two different brokers: long where the swap is favorable, short where the offsetting swap cost is low or where the pair also pays a positive swap on that side. Because the two positions are the same size in opposite directions, the price risk is hedged across the two accounts, and the net swap is your edge.
A swap-free account charges no overnight swap. The idea is to place the side that would normally pay a negative swap on the swap-free account, and the side that earns a positive swap on a normal account. The negative side costs nothing, the positive side earns, and the direction is hedged. This is the most talked-about form, and also the one brokers have countered most aggressively.
| Variant | Where the edge is | Main constraint |
|---|---|---|
| Cross-broker | Difference in swap pricing between two venues | Markups, basis between brokers, margin on both sides |
| Swap-free account | No swap charged on the paying side | Admin fees after a few days, and terms-of-service bans |
| Triple-swap timing | The 3x midweek rollover credit | Requires a genuinely positive net swap to begin with |
The whole strategy lives or dies on one number: the net swap after every cost, expressed as an annual rate on the capital you tie up. It is easy to be fooled by a positive swap on one side while ignoring the cost on the other and the capital locked on both.
# Net daily swap on the hedged pair (per lot) net_swap_daily = swap_earned_side - swap_paid_side - any_admin_fee # Annualize against the capital used on BOTH sides # (margin + buffer at both venues), not just one net_APR = (net_swap_daily * 365) / total_capital_committed # The trade is only real if net_APR is positive # AFTER markups, admin fees, and the cost of parking capital twice
The reason most swap-arbitrage ideas fail on paper is that people compute the earning side and forget the paying side, the admin fee, and the fact that capital is committed at two venues at once. A gap that looks like free yield often nets close to zero once all three are included.
Swap arbitrage extracts money from the broker’s rollover book, so brokers have built a full set of countermeasures. Understanding them is the difference between a strategy that lasts and one that is closed in a week.
| Countermeasure | What it does to the trade |
|---|---|
| Swap markups | Widen the spread on rollover so both sides tend negative, erasing the gap |
| Swap-free admin fees | Charge a fixed fee after a few days on swap-free accounts, replacing the swap they waived |
| Swap-rate adjustments | Change rollover rates with little notice when a pattern is detected |
| Terms-of-service bans | Most brokers explicitly prohibit swap and rollover arbitrage and can void profits |
| Execution filtering | The same toxic-flow handling used against other arbitrage can degrade fills |
Even where a broker tolerates the strategy, swap arbitrage carries structural risks that a price-neutral label can hide.
The hedge is only as good as the pricing match. If the two brokers quote the pair slightly differently, the offset is imperfect and a small basis risk remains. Capital is committed on both sides, so margin calls at either venue can force a liquidation that breaks the hedge and leaves you directionally exposed. And the edge itself is unstable, because swap rates change with central-bank policy and broker discretion, so a position that is positive today can turn negative without warning. None of these are reasons to avoid the strategy, but they are reasons to size it carefully and monitor it daily.
Swap arbitrage begins with data, not with a trade. You need the current overnight swap rates for the same pairs across the venues you can access, on both the long and the short side, plus any swap-free admin fee schedule. Then you screen for pairs where the net swap after all costs is clearly positive, and you re-check them regularly because the rates move. This is exactly the kind of tedious, repeatable comparison that a scanner does better than a human: pull the swap tables, compute the net-APR per pair, and flag only the combinations that clear a sensible threshold. The same measurement discipline we apply to broker execution applies here: do not trust the advertised number, compute the net figure yourself.
It is not illegal, but it is prohibited by the terms of service at most brokers, which can void the profits or close the account. Swap-free accounts in particular are intended for traders who need them for religious reasons, not as an arbitrage tool. Always read the specific broker’s terms before attempting it.
The carry trade holds a high-interest currency and takes the full directional risk of the exchange rate. Swap arbitrage hedges the direction with an offsetting position, so it captures only the rollover gap and not the price move. One is a directional bet with a yield, the other is an arbitrage on the swap itself.
It can, but the window is narrow. Broker swap markups, swap-free admin fees, and terms-of-service bans have closed most of the easy gaps. Where it works, it is a slow, capital-driven edge that requires careful screening of net-APR after every cost.
To account for weekend settlement, most venues apply three times the normal swap on one midweek day, commonly Wednesday. It amplifies whatever the net swap already is, positive or negative, but does not create an edge on its own.
More than a single-venue strategy of the same size, because you must fund margin plus a buffer on both sides at once. Since the per-trade edge is small, the strategy only makes sense with enough capital that the net-APR is meaningful relative to the operational effort.
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Swap arbitrage only exists after markups and fees. Learn how brokers price and filter the flow, and measure the real numbers yourself.