Margin checking: the 1-item probe

You cannot see the order book, so you poke it. Buy one unit at a silly high price, sell one unit at a silly low price, and the two fills hand you both edges of the live spread. It takes about thirty seconds and it costs real gold, which is exactly why most people do it wrong.

A margin check is the only way to read the current state of a market directly rather than inferring it. Charts and volume tell you what has happened. A probe tells you what is sitting on the other side of the glass at this exact moment, which is the number your flip will actually be priced against.

What the probe actually does

From lesson 1: a buy placed above existing sell offers executes at the lowest one and refunds you the difference. So if you offer to buy a single unit at a price nobody would ever ask, you are guaranteed to trade against whatever the genuinely lowest ask happens to be, and the amount you actually spent tells you what that ask was.

The sell side works the same way in reverse. Offer a single unit at a price nobody would ever accept and you trade against the highest resting bid, receiving more than you asked for. The amount you received, before tax, is that bid.

Two numbers, measured rather than guessed. The gap between them is the live spread, and after tax it is what a flip in that item is worth right now.

The procedure

1. Pick the item and open a buy offer for quantity 1.
2. Set the price well above the guide value. A comfortable rule is roughly 10% over on a normal item, more on something volatile. You are not paying it, you are just reaching past the whole ask stack.
3. Collect. The gold refunded tells you the real price paid.
4. Immediately open a sell offer for that same single unit, priced well below the guide value.
5. Collect. The gold received, before the tax line, is the highest bid.
6. Write both numbers down before you place the real offer, because they move.

Do the sell leg straight away. The value of a probe decays with every second, and a check you ran twenty minutes ago on a busy item is a historical fact, not a live one.

What it costs, with the tax

The probe is not free. You cross the spread in both directions, and you pay the 2% Grand Exchange tax on the sell leg, rounded down, capped at 5,000,000 gp per item.

That is the honest framing. A margin check is not an expense, it is the price of information, and the information is worth having exactly when it stops you doing something expensive. Thirty five thousand gp to avoid committing 56 million into a dead spread is a bargain. Thirty five thousand gp spent idly on nine items you were never going to trade is just a leak.

The cheap end and the 50 gp line

Below 50 gp per item the tax is under one coin, rounds down to zero, and is not charged at all. Probing a cheap rune or an arrow costs you only the spread, which on those items is a few gp. You can check twenty of them for the price of a single whip check.

There is a catch that has nothing to do with money. On very cheap items the price ladder is coarse, so the spread you measure is often one or two gp and rounding dominates everything. A probe that returns "bid 42, ask 42" on rune arrows is not telling you the market is broken. It is telling you the spread is smaller than the smallest unit the game can express, which means there is nothing there for a flipper.

The expensive end, where a probe hurts

On high value items the probe costs two things at once, and the second is the one people forget.

The gold cost scales with price. On Dragon claws at roughly 38M, the tax on the sell leg alone is around 760,000 gp, plus whatever the spread takes. On a Twisted bow at roughly 1.38B the tax hits the 5,000,000 cap, so the sell leg costs a flat five million however far the price climbs.

The limit cost is worse. Claws, Twisted bow and Ancestral hat all carry a buy limit of eight per four hours. Your probe consumes one of them. You have just spent 12.5% of your entire buying window on a measurement, and the four hour clock started ticking the moment that unit bought. On an item with a limit of five, such as the Arcane prayer scroll, a probe is a fifth of your window.

Five situations where a probe lies

A margin check measures one unit at one instant. Every failure mode comes from treating that one unit as representative.

1. The stack was one deep

Your buy filled at 798,000 because someone had a single unit listed there. The next four are at 812,000. Your measured ask was real and completely unrepresentative, and a large buy at your measured price will fill one unit and then sit. Volume on the item page is the sanity check here.

2. You moved the market yourself

On a genuinely thin item, your probe may have been the only trade in an hour. It repriced the item in the trade history, and if you then watch the guide value move you are watching your own footprint, not demand.

3. The market is mid move

A spread measured during a sharp move is a snapshot of chaos. Both edges are being redrawn while you type. If an item has just been named in an update, a probe tells you where the panic is, not where the price is going to settle.

4. The sell leg never filled

If your deliberately low sell offer sits there unfilled, that is not a failed probe, it is the loudest possible result: there is no bid at all near your price. Cancel it and cross the item off. An item with no resting buy side is an item you can enter and cannot leave.

5. You probed the wrong dose or variant

Potions, herbs and charged gear come in variants with connected buy limits, so a four dose and a three dose share one window. Probing one and trading the other tells you nothing useful and quietly halves your limit.

How GE Uncut keeps probes out of your record

A margin check looks exactly like a tiny losing flip: a buy, a sell, a negative number. Left alone it would poison every statistic you care about, dragging down your win rate and your average profit with trades you never meant to make.

So the plugin does not count them. When your synced history shows a sell of a single unit matched by a buy of that same item, on the same account, within a minute of each other, GE Uncut treats the pair as a price probe and quarantines it. The pair never becomes a position, never touches profit and loss, and never touches the win rate.

It is not deleted either. Both events stay in the ledger and the pair appears in History, because your in game trade history shows margin checks too and anything that vanished from ours would resurface later as a phantom missing trade. If a pair really was a genuine one unit flip rather than a check, the Restore button on that row puts it back into your flips as a completed trade with the normal maths.

The practical upshot: probe as much as you need to. Your recorded performance stays a record of decisions, not of measurements.

A routine that scales

Probing everything is a good way to spend a session paying tax. A workable order of operations puts the free information first.

• Shortlist without spending. Use the Flip Finder or the Margins board to get from thousands of items down to the handful that plausibly have room today.
• Check volume before you probe. An item that trades a few hundred times a day cannot support a large position no matter how wide the measured spread looks. The board's Trades/h column answers this for every row at once, which is faster than opening anything.
• Read the freshness columns first. Last buy and Last sell say how long ago each side actually traded. A row where the sell side has not moved in forty minutes will usually fail the probe in exactly the way described above, so you can skip it and keep the tax.
• Probe the two or three you would actually trade. Not the ten that look interesting.
• Re-probe before the sell leg on anything slow. If your buy took an hour to fill, the bid you measured an hour ago has moved.
• Keep the numbers. Yesterday's measured spread on the same item at the same hour is a genuinely useful prior for today.

For a single item you already have in mind, search goes straight to its page, where the live buy and sell prices, the chart and the daily volume sit together. That page will not tell you where the resting bid is to the gp, which is why the probe exists, but it will usually tell you whether probing is worth two taxed trades. Asking the assistant does the same job in a sentence when you are already mid-session and do not want to leave what you are doing.

Keeping the numbers, the last item on that list, is easier if you track the flips you do take. My Flips holds each position from the moment you place it until the last unit sells, so the gap between your measured spread and what you actually realised is recoverable later rather than something you half remember. That comparison is where a probing habit turns into judgement: after a few weeks you know which items reliably trade near their measured spread and which ones always disappoint, and those are the items worth probing at all.

You now know both edges of the spread. The next question is where inside it to put your offer, which is where a single gp starts to matter enormously on some items and not at all on others.

Item pages used above

Live prices, volume and buy limits for the items in this lesson: Abyssal whip, Dragon claws, Twisted bow, Arcane prayer scroll and Rune arrow.

GE Uncut is an unofficial, fan-made tool, not affiliated with or endorsed by Jagex Limited. RuneScape and Old School RuneScape are trademarks of Jagex Limited; in-game content and item images are the property of Jagex Limited, used for reference only. Price data is from the OSRS Wiki real-time prices API. See data attribution.