Lay odds

A layer takes the bookmaker's side. If the selection loses, the layer wins the backer's stake. If it wins, the layer pays the backer's winnings, so the risk is the liability, lay stake × (lay odds − 1). Laying 10 units at 4.0 carries a liability of 30 units, which the exchange holds until the market settles.

Lower is better for a layer, the reverse of backing, because a lower price means a smaller liability for the same stake. On a busy exchange market the best lay price sits a little above the best back price, and matched betting looks for bookmaker back prices that come close to it.

The lay price also sets the cost of a matched bet. Against a 10-unit back bet at 3.0 and 2% commission (use your own rate), laying at 3.1 costs 0.45 units whichever way the result goes, and laying at 3.2 costs 0.75. That is why an oddsmatcher reads the lowest lay price first.

In the OddsRelay feed

In the feed, lay prices sit beside the back prices they cover. On the matched feeds each outcome's lay is sorted lowest price first, and every offer carries exchange, price, available (the money available at that price) and link. On each-way and extra-place, lay is an object of two such arrays, win and place, and dutching has no lay. The prices come from the four exchanges the feed pairs against, Betfair, Smarkets, Matchbook and BETDAQ.

For exchange prices unpaired, GET /v2/odds/raw lists each exchange's outcomes with back_price, lay_price and available side by side, with no commission applied. includeLiquidity=false leaves out available, and exchangesOnly=true returns the exchanges alone.

A lay price holds only for the money behind it. If available is less than the lay stake, the rest waits unmatched or goes at a higher price, which raises both the liability and the qualifying loss. A tool that compares its lay stake with available before showing a pair saves its users that surprise. Where oddsFormat=american is accepted, lay prices come in that format too, and meta.odds_format says which one a reply carries.

From the blog

Related