> For the complete documentation index, see [llms.txt](https://docs.strikelabs.app/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.strikelabs.app/api-reference/tick-and-lot-size.md). # Tick and lot size ## Prices Prices are carried as integer micros — millionths of a dollar. That is the resolution of the engine, and it is finer than anything you will want to quote into. Prices you send are converted on arrival; a price with more precision than a micro is truncated to it. There is no enforced tick grid. A price of `0.415` is accepted and rests at `0.415`. In practice the house maker quotes in cents, so a book will normally look like a penny market. ## Quantities Quantities are also integer micros, so **fractional contracts are permitted**. `qty: 0.5` is a valid half contract. There is no minimum lot. A quantity of zero or less is rejected with `bad qty`. ## Prices must be positive A limit price of zero or less is rejected with `bad price`. To sell at any price, send a low positive limit rather than zero — an option can trade at a penny, so zero is not a meaningful floor. ## Market orders Omit `price` and the order crosses whatever is resting: ```json { "seriesId": "NVDA-1786492800-C-221", "side": "buy", "qty": 5 } ``` An order with no price never rests. If the book is thin it fills what it can and the remainder is cancelled, which returns `status: "partial"` with a `restedQty` of `0`. Against an empty book you get `no liquidity`. ## Fees The taker pays **50 bps of premium notional**. The maker pays nothing. ``` fee = premium × qty × 0.005 ``` Buying 2 contracts at $0.96 is $1.92 of premium and a fee of about $0.0096. The fee is checked before the order is accepted, so buying power accounts for it up front rather than surprising you at the fill. Fees are charged on premium, not on the underlying's notional. A deep out-of-the-money option costs almost nothing to trade. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.strikelabs.app/api-reference/tick-and-lot-size.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.