Partial closes and the hidden spread

[Shadow Trader]

Closing half a position at the first target and letting the rest run is a popular technique. The mechanics carry costs that are easy to ignore.

Each partial close is a separate transaction. On a spread-only account, the cost is embedded in the exit price. On a commission account, the closing commission may be charged on each closed portion, and some brokers apply minimum commission per transaction. Several small closes can cost more than a single full close.

In netting mode, a partial close reduces the position size and may leave the remaining volume at an average entry price that differs from expectations.

Another quirk: some platforms or brokers have minimum lot steps, so closing half of 0.03 lots isn't possible. Rounding then makes the partial close inexact.

A short test on demo, then on tiny live size, shows exactly how the partial close appears in the history and what it costs.

It's also worth recalculating expectancy with the extra costs included, since the technique's apparent benefit can shrink.

Some traders avoid the issue by entering in two separate orders from the start, each with its own target. That makes the position structure explicit and avoids rounding problems, though it does mean paying the entry commission twice on some account types.

How does the broker handle partial closes in cost terms, and was the benefit still there after the fees?