Every prediction market contract has an expiration date, but the way that expiration actually works swings wildly across platforms and contract types. Those mechanics create patterns that most participants walk right past, and a smaller group learns to lean on them.
Time decay looks like options, until it doesn't
Prediction market contracts have something in the neighborhood of options theta decay, but the dynamics run differently. An option bleeds time value as expiration approaches because there's less runway for the underlying to move. A prediction market contract can gain or lose value near expiration depending entirely on where the information is heading.
With no new information, prices tend to drift toward wherever they already sit, not toward 0 or 1. A contract parked at $0.60 for weeks with nothing new usually stays near $0.60, because nothing showed up to reprice it. You get long stretches of stagnation that snap the moment resolution-relevant news lands.
The final days are where it gets interesting. If the outcome is still genuinely uncertain, the trade flow goes bimodal. Some people are closing out to dodge resolution risk. Others are opening fresh positions because they think the last scraps of information hand them an edge. Volume spikes. Spreads either tighten as market makers fight over the closing flow, or blow out as they back away from being wrong at the buzzer.
Rolling expiration vs a fixed date
Some platforms use fixed expiration dates, so the contract resolves on a set day whether or not the outcome is already obvious. Others resolve on the event itself, which can land months before the nominal expiration.
That gap changes how you trade. A fixed-date contract that could resolve early carries the possibility of an early payout, so it trades differently. If a contract on whether a CEO resigns in 2026 might settle in January, you can't just discount it like a full-year hold. Early resolution means your capital could come back sooner, and that reshapes the effective annualized return.
Event-based contracts with no fixed date bring the opposite headache, which is capital lockup you can't size. You put on a position figuring it clears in three months, then the event keeps slipping. That's a regular occurrence in legislative and regulatory markets, where deadlines get missed as a matter of routine.
Expiration clustering and where capital rotates
When a batch of high-profile contracts expire around the same date, you get capital rotation. Resolved contracts hand capital back to traders, and that capital goes looking for the next active market. The receiving markets can get a bump in volume and price that has nothing to do with the underlying probabilities changing. Money just needed somewhere to go.
You can front-run some of this by tracking the major expiration calendar. After a big election contract settles and returns millions, the next most liquid category tends to pick up volume and tighten spreads over the following days. Being positioned in those markets before the capital shows up is a small edge, but a fairly consistent one.
Binary vs scaled resolution
Most contracts are binary and settle to 0 or 1. Some platforms run scaled contracts that resolve anywhere in between based on a number. A GDP-growth contract might pay linearly off the actual growth rate instead of a plain above-or-below-threshold outcome.
Scaled contracts have smoother risk profiles and messier pricing. The expected value depends on the full distribution of outcomes, not just which side of a line the number ends up on. That makes them harder to price, which also means the market has a harder time pricing them right. More room for anyone who can actually model the distribution.
Before you put money on it
Whenever I look at a prediction market position, the mechanics get mapped first. How does the contract resolve? When does it resolve? What happens if the event never occurs by the expiration date? Those details set your maximum capital lockup, your worst case, and the timeline on getting paid. Skipping them is like trading options and never checking the expiration date, which is to say you're guessing.