Glossary / Books & exchanges / Lay
A ParlayAPI glossary entry

Lay

To lay an outcome on an exchange is to bet against it - effectively acting as the bookmaker for that bet. The layer receives the backer's stake if the outcome fails, and pays out at the agreed odds if it succeeds, posting that liability up front.

Worked example

# Laying Team A at decimal 2.30, backer stakes $100
        liability = (2.30 - 1) × 100 = $130   # posted as collateral
        if A loses:  you keep the $100 stake (minus commission)
        if A wins:   you pay the $130

Laying enables positions sportsbooks don't sell: betting against a single team without backing every other outcome, and trading out of an earlier back bet at a different price - the exchange equivalent of a hedge.

Where it shows up in ParlayAPI

A lay price is the mirror of a back price, so it slots into the same math: implied probability of the lay side is one minus the back side's (before commission). When exchange quotes appear alongside sportsbook prices in a comparison, lay depth is what tells you the market's real conviction against an outcome.

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