Underlaying & Overlaying

In a standard back-and-lay, the lay stake is chosen to equalise the result whether your selection wins or loses. Underlaying and overlaying are simple stake adjustments that shift which outcome is favoured. They do not create value by themselves; they redistribute it between outcomes and can be useful when the offer terms make one outcome more attractive than the other.

Underlaying uses a *smaller* lay stake than the equal-lay figure. This increases the return if your back bet wins and increases the loss if it loses. It is sometimes chosen when a win at the bookmaker has extra downside (e.g., rolling wagering requirements) and you prefer not to lose money if the selection wins.

Overlaying uses a *larger* lay stake than the equal-lay figure. This reduces or removes the loss if your back bet loses, but it costs more if your back bet wins. It is commonly used on offers where a back win triggers a bonus or refund (for example, a free bet on winners), so the extra loss on a win is covered by the promotion.

1) Use the standard calculator to obtain the equal-lay stake.
2) Decide which side you want to favour based on the offer terms (win side for underlay, lose side for overlay).
3) Use the lay type selector in the calculator to choose between 'Underlay', 'Standard' or 'Overlay'.

• Underlay: you want to avoid losing money if the selection wins (e.g., to minimise the chance of entering or extending rollover), or the win side carries extra operational cost.
• Overlay: the promotion rewards a win (e.g., free bet on winners, early-payout style offers), so shifting cost to the win side and keeping the lose side at £0 can be preferable.

• Underlay/overlay change the distribution of results; they do not increase expected value unless the offer terms make one side more valuable.
• Prices move: if odds change after you compute stakes, re-run the numbers.
• Partial matches: split or cancel unmatched lays rather than leaving exposure open.
• Keep stakes natural and consistent with account health.