Not paid Expenses

As others have said, you've likely just fallen between the cracks of a system that isn't designed to facilitate payments to people who aren't on the payroll. Trying to go through AP with an invoice is a complete and utter waste of time, I have to agree with almost everyone else here; supplier set-up in the private sector comes with a metric shıt-tonne of due dil and procedure. They'll ask the OP for a company registration number, a VAT reg number, a tax certificate and all manner of stuff they can't provide.

I agree that a good-natured hounding of whoever your line manager was at the time is the best approach here. Don't ask for a One 4 All card, though, they're shıte. Ask for a Perx reward card instead, it's basically a pre-paid Mastercard you can use anywhere that takes credit cards. So everywhere, basically.

Call them,no more emails.Get a name to deal with.No result then sit in their reception-if you can spare the time.Don't worry about reputational damage-you have been mislead by this company.No result-small claims court.

I would be very careful about harassing anyone or threatening them with court actions

The OP just finished an internship, presumably with the hopes they'll get a full time job out of it. Would you risk a well paying job for the sake of a few hundred

While they didn't do anything wrong, they'll be gaining a rep as a source of drama, and hiring managers tend not to like drama

Also if they do get a job with the same company, then it would be easier to work out some expense claim while inside than outside. They obviously can't claim for expenses outside their contract but it's likely their manager can authorise some extra rewards to compensate

OP, while it's a bitter pill to swallow, I'd recommend you treat this like a lesson. It sounds like your managers overpromised before they had the details sorted. In future, it would be better to try and directly charge travel expenses to the company or be 100% sure you'll be reimbursed

True, and to be clear I'm not advocating letting it go

My point is that the OP should consider the full implications of any action before they take it

Say they harass the manager and eventually get a cheque for a few hundred to cover expenses. A few months later they're turned down for a role in that company and have to start from scratch. A role where one weeks earnings would cover the amount they were seeking in compensation. Seems a bit like cutting off your nose to spite your face

I can say from recent job seeking experience that despite full employment, landing a professional job is still quite challenging. Companies seem to have externalised any kind of training and now expect candidates to have complete knowledge of their systems from day 1. In this context, burning bridges may not be the most effective solution

I'm very much in favour of employees standing up for themselves, but it's a lot more effective from a position of strength. Being an unemployed recent graduate doesn't seem like a position of strength

Of course if the OP has no intentions or opportunity to go back to their previous employer then I say have at it

Having personally gone through it myself, setting up suppliers for companies in the pharma industry is a pain in the ass. You need proof of their quality management systems (e.g. ISO9001), financial standing etc. and then usually needs to be approved by a central approvals department, usually in another country, whose attitude is generally "computer says no".

Actually someone mentioned vouchers. Many companies are giving vouchers to employees as Christmas bonus. That would be hassle free.

As others have suggested, talk to someone you had dealings with and ask them what is the proper invocation to get this paid. A voucher with wide applicability might well save you the money you need.

Another issue on this is, since 1st Janurary all valid expenses for travel and subsistence that are reimbursed tax free to an employee have to be reported to Revenue via ERR. So that's more work the employer will need to carry out as a business. You will need to be added to their payroll software and any valid receipts / claims logged to your employee card. And ensure the expense you are getting reimbrused for is a valid expense and allowable tax free.

Even if they give you the value in 'vouchers', that voucher may need to be reported via ERR also.

It's a tricky one given the systems in place now.

It's not as simple as, sending the money via Revolut. Every cent has to be accounted for given the op said it's a Pharma company.

Spend a few weeks making calls and emails daily and see any hop!