Single opt-in, abbreviated SOI, is a lead model in which a conversion is counted the moment the user submits the form — no email click, no SMS code, no confirmation step.
Definition
Single opt-in, abbreviated SOI, is a lead model in which a conversion is counted the moment the user submits the form — no email click, no SMS code, no confirmation step. It maximises the front-end conversion rate and raw lead volume because nothing stands between the submit and the payout event, but it delivers lower-quality contacts than double opt-in: the pool includes mistyped addresses, throwaway inboxes, and users who filled a form on impulse without real intent.
SOI suits offers where the advertiser has its own strong process for qualifying leads after the fact — a call centre that phones every lead in verticals like insurance, finance or nutra, or a scoring system that grades behaviour before spending on the lead. In those cases the advertiser can absorb a noisier top of funnel because it filters downstream, and it prefers the higher volume SOI provides.
In context
Because SOI leads are unvalidated, payouts per lead are lower than DOI and scrub rates — the share the advertiser rejects — are higher. The affiliate's real metric is not the submit count but the accepted-lead percentage: 1,000 submits at a 60% acceptance rate and a $4 payout is worth $2,400, the same as 480 DOI-confirmed leads at $5. Affiliates ask for the historical acceptance rate before scaling an SOI offer and treat a falling rate as a signal that the traffic mix or prelander has drifted toward lower intent.
The choice between SOI and DOI is set by the advertiser and reflects a volume-versus-quality decision. An affiliate cannot usually change it, but can choose which offers to run based on it: SOI when they have high-volume, lower-intent traffic and want a simple funnel, DOI when they have engaged traffic and can execute a clean confirmation step.
Running SOI traffic through a DOI offer, or vice versa, tends to produce a mismatch between what the funnel attracts and what the payout rewards.
Worked example
An SOI finance offer converts at 22% on the prelander to a submitted lead. The advertiser's call centre reaches and accepts 60% of those leads, so the affiliate's $12 per accepted lead works out to $7.20 per raw submit.
When a new prelander pushes submit rate to 28% but acceptance falls to 45%, effective revenue per visit barely moves and the affiliate reverts.
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