# NBBO Also written national best bid and offer. *https://stockmarketstack.com/glossary/nbbo · next to Stock Market Data APIs* **Definition:** The highest bid and the lowest offer available across all US venues at a moment, calculated and published by the securities information processors from the consolidated tape. It is one bid and one offer, not a book: no sizes behind the top, no venue-by-venue depth. It is the number regulation, brokers and clearing treat as the market price of a quote. ## How it works Every US venue publishes its own quotes. The securities information processors merge them and compute, continuously, the highest bid and the lowest offer anywhere in the market — the National Best Bid and Offer. It comes off the consolidated tape, which is what makes it the reference number: brokers, regulators and clearing all treat it as the price of a quote at an instant, and a print is judged against it. Three properties matter more than the definition. **It is a top, not a book.** One bid and one offer, with no venue-by-venue depth behind them. The tape historically carried round lots only, and did not carry depth at all. That is what the SEC's Market Data Infrastructure Rule set out to widen: odd-lot information reached the tape on the first business day of May 2026, and in an order dated 15 January 2026 the SEC exempted the plan participants from the odd-lot depth requirement until the first business day of May 2028. Depth of book remains a separate product bought from each venue. **It is derived, so it can be recomputed — and recomputed differently.** Anything that receives venue quotes can calculate a best bid and offer of its own from whatever subset it happens to receive. That number is not wrong, it is answering a narrower question, and it will sit inside or outside the consolidated NBBO depending on where the liquidity was sitting. **It is a separate, sizeable historical file.** NYSE's Daily TAQ client specification dated 3 March 2026 publishes typical sizes for one trading day of consolidated US equities: trades 2.4 GB across 69 million records, quotes 38 GB across 1.9 billion, and the NBBO file 11 GB across 330 million — all gzipped. The NBBO is roughly a sixth of the quote volume, because it only changes when the best price on one side changes. ## Where it shows up in options Options are the case where the phrase does most work. A single options underlier has hundreds of strikes and expiries across every OPRA exchange, so a chain is a large object and the bid and ask on each line are the part a reader acts on. Historical options files are normally sold as every print with the NBBO attached at trade time — the shape of [Cboe DataShop](https://stockmarketstack.com/tools/cboe-datashop) — and options-focused APIs such as [ORATS](https://stockmarketstack.com/tools/orats) return NBBO bid and ask alongside their own derived values. The [options data collection](https://stockmarketstack.com/collections/options-data) puts the question plainly: find out whether the bid and ask you are being sold are the NBBO or a snapshot of one venue. ## Why it matters here For anything that compares a fill, a backtest or a chart against "the price", the NBBO is the defensible number and a single-venue quote is not. Two consequences on this site. First, when a card advertises real-time quotes, the useful question is which plan or which venues are behind them. A quote from one venue on a thinly traded name can differ from the consolidated best by a visible margin, and a spread computed from it is not the spread anyone else saw. The [consolidated tape](https://stockmarketstack.com/glossary/consolidated-tape) entry covers where the number is assembled. Second, a program acting on the NBBO is non-display use, priced per firm rather than per screen, so the same number is cheap to look at and expensive to trade on. That split is the subject of [what real-time market data costs](https://stockmarketstack.com/guides/real-time-market-data-fees), and it catches more side projects than any technical limit does. ## Where you will meet this - [ORATS](https://stockmarketstack.com/tools/orats.md) - [Cboe DataShop](https://stockmarketstack.com/tools/cboe-datashop.md) - [FirstRate Data](https://stockmarketstack.com/tools/firstrate-data.md) - [Tick Data](https://stockmarketstack.com/tools/tickdata.md) - [AlgoSeek](https://stockmarketstack.com/tools/algoseek.md) - [ATAS](https://stockmarketstack.com/tools/atas.md) - [Bookmap](https://stockmarketstack.com/tools/bookmap.md) ## FAQ ### Is the bid and ask from my data provider the NBBO? Not necessarily, and it is the first thing to check. A best bid and offer computed from one venue's feed, or from a subset of venues, is a legitimate product and a different number — it will sit inside or outside the real NBBO depending on where the liquidity was. A vendor that is publishing the consolidated figure will say which plan it comes from. ### Does the NBBO show how much size is available? Only at the top, and historically only in round lots. It is one price on each side, so a thousand shares showing at the best offer says nothing about the next thousand. Depth of book is a separate, more expensive product bought from each venue, and the tape has only recently begun carrying odd-lot information at all. ## Sources 1. [Schedule of Market Data Charges](https://www.ctaplan.com/publicdocs/ctaplan/Schedule_of_Market_Data_Charges.pdf) — Consolidated Tape Association, 2019-02-06. The operative schedule — it is the file the CTA plan's own pricing page links, and it has not been restated since. 2. [Order Granting Temporary Exemptive Relief from Rule 600(b)(69)(ii) of Regulation NMS, Release No. 34-104612](https://www.sec.gov/files/rules/exorders/2026/34-104612.pdf) — US Securities and Exchange Commission, 2026-01-15 3. [Daily TAQ Client Specifications, version 4.3](https://www.nyse.com/publicdocs/nyse/data/Daily_TAQ_Client_Spec_v4.3.pdf) — New York Stock Exchange, 2026-03-03 *Last updated 2026-09-21. A reference page, corrected in place — not a dated post.*