A welcome offer is a paid advertisement with a price tag attached, and the price is in the terms. Seven clauses do almost all the work. Once you know which seven, checking an offer takes about two minutes.
This single line changes the value of a free bet more than any other, and it is the one most often skipped. With an ordinary bet, a winner pays you the stake back plus the profit. With most free bets, you get the profit only — the stake is consumed.
Illustration, not an offer: a €20 free bet at odds of 3.0. As a cash bet that pays €60 back. As a "stake not returned" free bet it pays €40. Same odds, one third less money, and the difference lives in four words in the terms.
Offers usually require the qualifying bet, the free bet, or both, to be placed above a minimum price. That does two things: it rules out the safe short-priced selections, and it pushes you towards bets you are more likely to lose. A qualifying bet placed below the minimum normally voids the offer quietly — you find out when the free bet does not arrive.
Ask whether anything won from the free bet can be withdrawn immediately, or has to be staked again a number of times first. Where a multiplier applies, the honest way to read it is: the money is not yours yet, and each round of re-staking gives the margin another bite at it.
Free bets expire, often within days, and the clock usually starts when the bet is credited rather than when you notice it. An offer you have to use by Sunday is an offer that decides for you what you bet on. That is the point of the clause.
Three of them recur: a maximum stake while a bonus is active, a maximum amount you can win from bonus funds, and a cap on how much of a big win is actually payable. A headline number can survive all three and still be much smaller in practice.
Many offers exclude certain e-wallets from qualifying deposits. Most also limit the promotion to one per person, household, device, IP address or card — which matters in a shared house, and matters more because breaching it usually voids winnings rather than just the bonus.
The banner is marketing. The binding text is behind the "terms apply" link, and often behind a second link from there to general promotional terms. If a clause you care about is not in the first document, it is usually in the second. If you cannot find either, treat the offer as unreadable and skip it.
Promotions are a customer-acquisition cost, and the people designing them model the return before they publish. The realistic way to read a welcome offer is not "free money" but "a discount on a product whose long-run price is still above zero". Some offers are better value than others, and that is worth knowing. None of them changes the direction of the margin.
Two habits that cost nothing. Check the clauses before you deposit, not after, because after depositing the sunk money argues for you taking the offer. And decide the amount you are prepared to lose before you read the number in the banner, because that number is chosen to move it.