The Cost Nobody Backtests: How Overnight Swap Quietly Decides a Daily-Timeframe System

Spread gets discussed endlessly. Swap almost never does — and for any system that holds positions overnight, swap is the cost that decides whether a modest edge survives.

Swap is charged or credited when a position is rolled over at the broker's end of day, and it is set per symbol by each broker, not by the market. Two brokers quoting the same instrument can apply materially different rollover rates, and Wednesday usually carries a triple charge. The Strategy Tester applies the rates in your broker's current symbol specification — today's rates, retroactively, across the whole history.

A scalper that closes within the session pays swap almost never. A daily-timeframe trend follower can hold a single position for weeks, so it pays the rollover dozens of times per trade. The same swap rate is negligible in one system and decisive in the other. This is why holding period, not timeframe alone, tells you how exposed a strategy is.

Rollover is asymmetric: one direction may pay you, the other charges you. A long-only or long-biased system on an instrument with negative long swap carries a permanent headwind that no entry logic improves. Check the swap on the side the strategy actually trades, not the average.

Run the backtest on the account you will actually trade, so the tester uses that broker's swap table. Then re-run it with swap set higher than your broker's current rate. If the result collapses under a moderate increase, the strategy is not trading an edge — it is trading a favourable financing rate that can be changed without notice.

Bitcoin Glacier is a daily-timeframe system that holds through long trends, so we say plainly in the description that you should confirm your broker's spread and swap on a demo account before going live. A rollover table is not a detail you check after purchase; for a position-holding system it is part of the strategy.

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