Do you spend your entire dinner stipend?

As another user said, these are typically (but not always) expensed to the client (obvious example is if a deal falls over - at least at my shop, we certainly don't send a client expenses if a deal falls away. In fact under our engagement letters I doubt we even have the right to. And we sometimes pick and choose which expenses to send to a client - travel for key meetings is usually essential, but printing, research, and late meals are often seen as a bit penny-pinching).

So, when a deal closes and we prepare the invoice. A VP or whoever will email the A/R team for an expense report, and that report shows each and every expense filed by each and every banker. Note that this is an XLS spreadsheet, and will say something like "John Smith - Late Meal - £23.45" (it won't show the itemised receipt - I presume one could request that but frankly that is a nosebleed level of pettiness). 

Usually someone will review the expense sheet to check for errors. A client can request itemised expenses in theory, and if it turns out we accidentally charged them for some unrelated MD's stay at the Mandarin Oriental in Singapore for our deal that took place entirely in the UK, that's a problem. So someone will (or should, at least at my shop) see how much you spent on late meals and how closely you kept to the threshold.

That said, while it miggggght raise an eyebrow if you're expensing for meals everyday for two consecutive weeks when the deal was definitely quiet, I can't imagine someone actually raising this. Especially when a 3-day stay at a midtown hotel in New York for a handful of meetings outweighs your entire dinner expenses for the deal. Or when research costs someone aggregate to some ungodly number. 

Does it impact reviews or bonuses? The only way I can see this happening is if your VP is outrageously vindictive and reviews your expenses and in their mind decides you were excessive and deicdes to use it against you when writing your review. Even then, I've been in review committees and if I were reading a review written by a VP that calls out dinner expenses, it says more about the VP than the AN to be honest. Bonuses are decided totally separately. You essentially (with some standard error that comes from the fact no one can read your mind) get paid the minimum amount needed to retain you. If you get zero, that isn't because of your dinner expenses.

Hope this sheds a bit of light on the topic, if probably way too much information. I've never in my career seen someone's expenses get challenged.