The arbitrage plan

The short version

So the plan is narrow on purpose: bet only locked pairs, at licensed books, above your after-tax break-even, after confirming both prices yourself, and record both bets. The Arbitrage finder applies these rules and its calculator shows the after-tax result for each pair.

What counts as an arbitrage here

An arbitrage is two bets at two sportsbooks where every final result pays back at least what you staked. The finder checks three shapes, and grades each one on every result that matters (the final margin, or the player’s or game’s count) rather than trusting a shortcut:

• Two-way: both sides of one line, such as Over 21.5 at one book and Under 21.5 at another, or each team’s moneyline.
• Middle: two lines that overlap, such as Over 24.5 and Under 26.5. Either way one wins, and a 25 or 26 wins both.
• Moneyline against a spread: one team to win and the other team +1.5. If the favorite wins by exactly one, both win.

Write p for a price’s break-even probability (100/(odds+100) for plus odds, odds/(odds−100) for minus odds, using the absolute value). If the two add to less than 1, stake each side in proportion to its p: for a total stake S, bet S × p₁ / (p₁ + p₂) and S × p₂ / (p₁ + p₂). A single winning side then returns S / (p₁ + p₂). A result exactly on a whole-number line refunds both bets.

A pair is Locked only when all of these hold:

• the two quotes were taken within five minutes of each other, before the game started;
• they are at two different sportsbooks;
• both books’ settlement rules for that market are on file and match (overtime, ties, a player who doesn’t play). Rules can be checked against the book’s published rules or assumed standard; assumed ones are labeled.

Anything else under 100% is listed under Check before betting with the reason. Pairs between 100% and 101% are near misses. Nothing on these pages feeds Today’s Picks or Market Watch.

What the last month shows

We replayed today’s rules over every saved NFL, NBA, NHL and MLB price snapshot from September 21, 2026, 5:45 PM EDT to October 22, 2026, 7:08 AM EDT. This is a paper exercise: saved quotes, not bets placed, and a quote can lag the book by a minute or more. Each pair is counted once, at the prices when it was first seen, with stakes split so both sides pay the same.

Of the 75 pairs seen in two or more snapshots, 30 involved an offshore book and 39 were MLB props, whose settlement rules are not on file; 6 were neither.

“Still there at the next refresh” means the pair appeared in at least two snapshots, the closest thing in this data to having had time to bet it. Scheduled snapshots are hours apart, so pairs that came and went between them are missing. MLB was half of the total and its regular season is over.

The largest pairs

After federal tax

The same pairs from scenario B, $1,000 each, in each pair’s worst result:

Taxes decide the threshold

Every winning bet’s profit is gambling income. Every losing bet is a gambling loss, and from tax year 2026 only 90% of losses are deductible, only if you itemize, and never more than your winnings. An arbitrage always has a losing side, so tax applies to more than your profit. For a pair with profit P whose losing bet was L, at federal rate t:

• itemizing: after-tax profit ≈ (1 − t) × P − t × 0.10 × L;
• standard deduction: after-tax profit ≈ (1 − t) × P − t × L.

With the losing bet about half the stake, the return a pair needs before tax just to break even is about:

State income tax raises these. Some tax advisers net results by session (one day at one book), which can shrink the drag for someone betting many pairs at the same books; ask yours how they report. We found no law restoring the full deduction as of October 22, 2026. This is an estimate, not tax advice. Sources: Tax Foundation, Kiplinger.

How to work it

1. Set up. Open and fund accounts at the licensed sportsbooks available where you are. Each pair needs money already sitting at both books, so plan on a balance at every book you use. Ask a tax professional whether you will itemize and at what rate, then set those in the finder’s calculator. The finder can hide pairs that involve offshore books; we recommend you do.
2. Pilot by hand, two to four weeks. Check the finder after each refresh. Bet only Locked pairs whose after-tax result is positive, at $100 to $250 per pair. Before betting, open both books and confirm the line and both prices. Place the bet at the book whose price stands out from the others first, because it is the one most likely to move, then the other side at the price shown or better. Track both bets in Bet Tracker with the finder’s Track buttons.
3. Keep score. Log every attempt, including the ones where the second price had moved, a book cut your stake or a bet was refused. The pilot’s question is simple: after failed attempts and tax, did it make money?
4. Scale only on evidence. Raise stakes toward each book’s limits only if the pilot was positive after tax. Books often limit accounts that only bet arbitrage; when one does, stop routing pairs to it.

When something goes wrong

• The second price moved. You now hold one side alone. Either take the other side at the best price still available, accepting a small loss, or decide up front that you will hold. Decide before you start, not in the moment.
• A bet is voided. If one book voids its side (a player scratch, an obvious-error price, a rule you missed) and the other does not, the remaining bet is unhedged. Matching settlement rules are why Locked requires them.
• Caps. Set a maximum per pair and a maximum total of unhedged bets per day, and stop for the day when it is reached.

What runs today, and what comes next

Running now

• Every NFL, NBA, NHL and MLB refresh scans its saved prices with the same rules, publishes the results to the finder and keeps a paper ledger of every pair seen.
• Scan now on the finder lets an editor rescan current prices on demand: game lines for every upcoming game in a league for about 3 Odds API credits, or one game with player props for up to 7. An option adds the feed’s second group of US books (Hard Rock Bet, betPARX, Bally Bet, Fliff and others) at twice the cost. Their rules are not on file, so their pairs start under Check before betting. Scans pause when credits fall to the reserve kept for the scheduled refreshes.
• The calculator splits any total stake and estimates the result after federal tax.

Next, in order

1. Read the rules we assume. Replace each assumed profile below with the book’s published rules, and add MLB batter and pitcher rules so those pairs can lock.
2. Alerts. Notify an editor when a Locked pair above the after-tax break-even appears, instead of waiting for someone to look.
3. Faster scans near game time. Most pairs vanish within an hour. A game-lines scan every 30 minutes across four leagues costs about 12 credits a scan; props cost far more and need a budget decision.
4. Alternate lines and more books. Middles need alternate lines, which we do not fetch on schedule today. More books mean more pairs, at more credits.
5. Prediction markets. Kalshi contracts are observed separately, and a comparison needs an exact, verified outcome match. An NFL tie pays 50¢ there, while a two-way sportsbook moneyline is normally refunded.

Sportsbook rules we rely on

Two prices form a pair only when both books grade the bet the same way. A market group with no profile on file sends its pairs to Check before betting. Rules can differ by state and by market name, so confirm them with both books.

Assumed industry-standard rules, set 2026-10-22 when the multi-sport arbitrage scan launched, following the NHL treatment (owner decision 2026-10-06). Not yet checked against each book's published rules. Remove a book or market group here to send its pairs to Check before betting; replace each assumption with a source once its rules are read. Rules version arbitrage-rules-2026-10-22+nhl-standard-2026-10-06.

NFL

• fanatics: Not yet on file, as for NHL; its pairs go to Check before betting.

NBA

• fanatics: Not yet on file, as for NHL; its pairs go to Check before betting.

NHL

• fanatics: verification in progress; until it is complete, Fanatics prices are shown but treated as unverified.

MLB

• batter and pitcher props: Books differ on whether a batter must start or only bat once, and on listed-pitcher voids. No player profile is on file, so every MLB prop pair goes to Check before betting.
• offshore game lines: Offshore books may default to listed pitchers, which voids one side if a starter changes. Not on file.

What the profiles mean

• Includes overtime; a tied moneyline is refunded (NFL): Moneylines, spreads and totals are graded on the final score including overtime. A two-way moneyline on a game that ends tied is a push.
• Overtime counts; void if the player doesn't play (NFL): Player props count the whole game including overtime. A player who does not play is void, not a loss.
• Includes overtime (NBA): Moneylines, spreads and totals are graded on the final score including overtime.
• Overtime counts; void if the player doesn't play (NBA): Player props count the whole game including overtime. A player who does not play is void, not a loss.
• Includes overtime and shootout (NHL): Game bets (moneyline, puck line, total) are graded on the final score including overtime and the shootout; a shootout win adds one goal to the winning team's score.
• Overtime counts, shootout does not; void if the player doesn't play (NHL): Player props count statistics from regulation and overtime, not the shootout. The player must take part in the game; a player who does not play is void, not a loss.
• Action; official after 5 innings (MLB): Moneylines stand whoever pitches and are official after five innings (4½ if the home team leads). Run lines and totals need nine innings (8½ if the home team leads).

Kinds of sportsbook

• Licensed: Licensed by US state regulators where it operates.
• Offshore: Not licensed by any US state. Legal, payout and account risks are yours.
• Sweepstakes: A sweepstakes or social sportsbook, not a state-licensed sportsbook.