Basic order types

Two primitives — market and limit — plus the modifiers that control how they behave. Everything in Advanced order types is built from these.

Market and limit

A market order executes immediately against the best available prices. You get the fill; you do not get to choose the price. In a thin book, the last part of a large market order can fill far from the first.

A limit order sets the worst price you will accept — the maximum when buying, the minimum when selling. It fills at your price or better, or it rests on the book until it does. Control over price, no guarantee of a fill.

Time in force

Value	Behaviour
`GTC`	rests on the book until filled or cancelled — the default
`IOC`	fills whatever it can immediately, cancels the rest
`FOK`	fills completely and immediately, or not at all
`GTX` / post-only	rests, but is rejected if it would take liquidity

Use IOC when a partial fill now beats a complete fill later; FOK when a partial position is worse than none — one leg of a spread, for instance. post-only guarantees the maker fee rather than the taker fee, at the cost of being rejected when the market moves into you.

Modifiers

Reduce-only — the order may only shrink an existing position, never open or flip one. This is the safe way to close: if the position is already gone, the order is rejected rather than quietly opening the opposite side. Reduce-only orders also stay permitted when opening is restricted, such as on equity markets outside US hours.

Post-only — reject rather than take. Equivalent to GTX.

Slippage tolerance — on market orders, the maximum deviation you accept, with a behaviour to match:

Behaviour	What happens when the bound is hit
`partial_fill`	fill what fits inside the bound, cancel the rest
`reject_all`	cancel the whole order
`warn_only`	fill anyway and flag it

On options, the equivalent is a maximum slippage in basis points of mark. Set it. Without it the only protection is the venue price band, which is a fat-finger guard, not an execution guard — and options books are frequently one-sided.

Price bands and grids

Rule	Perpetuals	Options
Limit price band around mark	±15%	±30%
Price increment	per-market tick size	per-contract tick size
Size increment	per-market step size	per-contract lot size
Minimum order	per-market minimum size	minimum size and minimum premium notional

Off-grid orders are rejected, not rounded. On options, tick size varies contract by contract within the same expiry — read it from the contract rather than assuming one value for the chain.

Position exits

Every perp position can carry a take-profit and a stop-loss that the exchange monitors and executes for you, as market closes. Options positions carry exits too, but quoted on the underlying's price rather than the premium — see Options.

A position may only be protected by one engine at a time. If a bracket or OCO already guards it, setting a position-level take-profit/stop-loss is refused until you explicitly replace the existing protection.