The commonest way to lose a bonus is to be ineligible before you start, and the commonest reason is that the bank you are switching to shares a group with one you already use — or one you took a bonus from years ago.
The two questions banks actually ask
First: do you already hold an account with us? Most offers are for new customers, and some count anyone who held an account on a particular date years ago — HSBC looks back to 2023, NatWest to a date in 2026, and those dates move.
Second: have you had a switch bonus from this group before? Usually that is a permanent exclusion rather than a cooling-off period.
Only you know the answer to the second question. No app can look it up, and a wrong answer produces a plan that cannot pay.
What we do about it
The app asks which banks you hold and which bonuses you have taken, then applies the group rules for you — including picking the better of two offers inside one group, and letting you swap to the other if its pay-in is easier. Where a bank has a date-based rule it cannot check, it tells you what to go and confirm before you do the work.