Guide 11.4
Intermediate, 7 min read. Checked with Scalpel 1.12.8 on .
In short
The Risk tab holds your SIM account (a $25,000 starting balance, no slippage, IBKR Pro Tiered commissions by default) and the kill-switch caps that block orders: a $250,000 fat-finger cap per order, a $250,000 cap per position, and a $1,000 daily loss limit that locks new entries when it is hit. Auto-flatten is off by default. Set the caps to fit your own account before you trade LIVE.
The caps sit in front of every buy, in SIM and LIVE. They never shrink an order: an order that breaks one is refused with a toast saying which. Open Settings (Ctrl+,) and pick Risk.
| Option | What it does for your trading | Default | Allowed values | When to change it |
|---|---|---|---|---|
| SIM start ($) | The cash a fresh SIM account starts with, and what Reset SIM account puts it back to. SIM is a cash account: a buy bigger than your free SIM cash is refused. | 25000 | Whole dollars | Set it to the size of the account you will trade LIVE, so your SIM habits fit your real buying power. |
| SIM slippage (c) | Makes SIM fills worse by this many cents a share: buys fill higher, sells lower. 0 fills at the book price. | 0 | 0 to 99 cents | 1 or 2 gives a more honest paper P&L on thin, fast stocks. |
The note reads: "SIM slippage makes fills pessimistic by N cents per share (buys higher, sells lower). 0 = frictionless fills at the book price."
SIM estimates the fee on every fill so your paper P&L is net of costs. LIVE always uses the commission Interactive Brokers reports.
| Option | What it does for your trading | Default | Allowed values | When to change it |
|---|---|---|---|---|
| Commission plan | Fills in the three numbers below for your IBKR plan. Shows Custom when they match no plan. | IBKR Pro Tiered | IBKR Pro Tiered, IBKR Pro Fixed, IBKR Lite, Custom | Pick the plan your IBKR account is on. |
| Comm $/share | Dollars per share. | 0.0035 | A decimal | Only on Custom. |
| Comm min ($) | The least an order is charged. | 0.35 | A decimal | Only on Custom. |
| Comm cap (% of trade) | The most an order is charged, as a percent of its value. 0 removes the cap. | 1 | A decimal | Only on Custom. |
The fee per fill is the larger of per-share x shares and the minimum, capped at the percent of the trade's value:
| Plan | Per share | Minimum | Cap | Exchange and clearing fees added |
|---|---|---|---|---|
| IBKR Pro Tiered (default) | $0.0035 | $0.35 | 1% | Yes |
| IBKR Pro Fixed | $0.005 | $1.00 | 1% | No (included in the price) |
| IBKR Lite | $0 | $0 | none | No |
| Custom | yours | yours | yours | Yes |
On Tiered and Custom, SIM adds the fees IBKR passes through: $0.003 a share on fills that take liquidity (0.3% of the value under $1) and $0.0002 a share clearing on every fill. A 1,000-share scalp at $4 on Tiered costs $3.50 in commission plus $3.20 in fees each way. Which plan suits you is in guide 6.3.
| Option | What it does for your trading | Default | Allowed values | When to change it |
|---|---|---|---|---|
| Fat-finger ($) | Refuses any single buy whose dollar value is over this: "Order exceeds the fat-finger cap". Catches a wrong preset or a stray zero. | 250000 | Whole dollars | Set it a little above your biggest normal order, for example $20,000 on a $25,000 account. |
| Max position ($) | Refuses a buy that would take your position in one symbol past this value: "Position would exceed the max". Adds to an existing position count. | 250000 | Whole dollars | Set it to the most you ever want in one stock. |
| Daily loss ($) | When the day's realized plus unrealized P&L falls to minus this, a RISK LOCK banner appears and new entries are blocked. Exits, stops and Flatten All still work. The day runs from New York midnight, in SIM and LIVE, and counts trades closed before a restart. | 1000 | Whole dollars; 0 turns it off | Set it to the loss that ends your day, often 2 to 3 times your normal risk per trade. |
| Auto-flatten on daily loss | When the daily loss trips, also sells every open position on every desk at once (in LIVE crossing about 1% through the price). | Off | On or off | Turn it on if you would rather be taken out than decide in the moment. |
The banner's Resume trading button lifts the lock; switching between SIM and LIVE lifts it too. After a resume, the lock comes back only if the day's loss grows by another quarter of the limit (with a $1,000 limit, $250 deeper than where you resumed), or on a new day. The full walkthrough is in guide 7.1, and the caps in guide 7.2.
The caps are a seatbelt, not a strategy. Fast small-cap momentum trading carries a significant risk of loss and is very difficult, and most people who try it lose money. A daily loss limit you respect, and small fixed risk per trade, are what let you keep learning.
A trader with a $25,000 account who risks $100 a trade might set Fat-finger ($) 15000, Max position ($) 20000, Daily loss ($) 300 and turn on Auto-flatten on daily loss. A Risk (Cents) $100 entry at a 10c stop on a $9 stock asks for 1,000 shares, $9,000: allowed. The same at a 5c stop asks for 2,000 shares, $18,000: over the fat-finger cap, so it is refused rather than shrunk. More in guide 14: settings for a small account.
Reset SIM account wipes the SIM ledger: cash back to the SIM start ($) shown on the tab, positions, orders and closed trades cleared, and any SIM risk lock lifted. It asks once: the first click turns the button into Confirm reset to $25000, the second resets. It never touches LIVE: pressed while LIVE is showing, it resets only the SIM account and your LIVE positions and orders stay on screen.
Changes apply to the running session when you click Apply or press Enter.