My personal experience has been that companies who give signing bonuses usually have retention issues and the bonus has to be paid back if you leave within a year. At least that was the experience when I graduated college. After becoming an experienced hire I haven’t been offered one.

It can vary by company and culture. Tech may be different, but in non-tech roles where equity isn't expected in most roles, signing bonuses can serve a function to nudge someone to leave a role they're comfortable in, or to make up for other aspects the candidate is losing out on by leaving at a certain time (e.g. annual bonus with 10a 10% of salary target pays out in March, but the new company wants you to start in January).

No, that's why the GP wanted it.

It 100% doesn't matter either way, as those bonuses always come with attrition requirements - you have to pay back all or part the bonus if you leave the company before some predetermined time period. If you don't agree to the payback terms then you simply don't get the bonus.

So a bonus paid before you start is more-or-less identical to a bonus paid with your first paycheck. You don't get to keep it if your offer is rescinded or you don't show up on your first day.

Thanks, but maybe I should have worded it better: is a bonus just for starting your job common? I've never heard of this in the UK applying myself or hiring. Only yearly bonuses for performance

Not common but also not unheard of, it's simply just an advance on your paycheck.

I've seen them be offered in jobs/industries/companies where there is a labor shortage or the job is difficult to fill for some reason. They might be standard-ish in some jobs/industries.

like I said, you'd almost always be required to stay for X amount of time - like a year plus usually, or you gotta pay some or all of it back.

Yes, they’re not uncommon, across a wide range of job types. I recently got a signing bonus for a part time job as an EMT for instance. In tech especially they can be quite large to offset stock options or bonuses the employee is giving up by switching jobs. If I’m about to be poached right before my annual bonus of x thousand pays out, I’ll want a comparable signing bonus.

There are signing bonuses in the UK. I think you will be very unlikely to get it immediately on signing though - it's usually within the first couple of months of employment or with your first salary, something like that.