Hi there!
It’d be sweet to be able to categorise a vendor into different categories. For example, I shop at Tesco for groceries, and this rightly goes into the Groceries category. But sometimes, I also pick up a sweet £3 meal deal for lunch, and I’d love to be able to categorise this transaction as “Eating Out”.
Perhaps when you go into a transaction, you could be able to change the category without it affecting all transactions with that vendor.
As in Weatherspoons with beer and food could be entertainment or eating out?
I think my example expanding on @johnmallon’s might help - sometimes I’ll go into Tesco for my grocery shopping and it’ll rightly be categorised as groceries. However, another day I may have to go to Tesco and grab fruit or some random stuff which I would claim back from work (/ student society in my case) - this transaction would be an expense instead. It could be the same goods - but still a different category.
I could start trying to think of some more obscure ones:
This could get even worse in places like Japan where the same convenience store terminal could make transactions that fit in to every single category! 
Thankfully, it can all be categorised in to holidays or expenses for us travelling there from the UK.
Unless I’m misunderstanding, can this not be done already? For example with iTunes, I’ve categorised my Apple Music subscription transaction (£9.99 one) as a bill, and me buying other stuff as entertainment across different transactions. 
I think some of the problem comes from where Monzo tries to learn from the transaction. My Sainsbury’s transactions are seemingly random between being automatically marked as eating out or groceries because I have an approximately equal number of café and regular shop transactions. I have to change it maybe 75% of the time.
Maybe there should be some form of intelligent time based automation when if comes to supermarkets.
i.e. if its between 11-2 in the day and you spend less than £10 it goes into eating out category because it guesses that it is lunch, but if it is over say £20 at any time it assumes that it is groceries. (I am just making these figures up as an example)
While this would not completely fix the issue and you may still run into some problems, I think it would fix a lot of causes of this bug.
My example is getting a lunch from Tescos one day, changing the category to eating out. Then doing a weekly shop at Tescos that evening spending over £100 and suddenly seeing that my eating out was £100 over what I was expecting.
Mine are nearly always transport because of the petrol station - I just have to remember to reclassify it as groceries when I do shop there.
You’ve nailed it @RichardR, that’s exactly what happens.
Our current way to “learn” about your categories is still a bit naive so this kind of exceptions happen. I’m sure we’ll improve it in the future so we learn about your actual patterns. Plus the usual sci-fi that I always like to dream about… something that could imagine that a £3 transaction at 12:30AM in Tesco is probably a meal deal and not groceries 
I like the learning concept in theory but it does cause real problems when trying to get to totals for transactions that’s been tagged with emoji / keywords (to create sub-categories) because the suggested tags can’t be edited or filtered out of the search results. Would adding either of those options be possible?
I’ve just noticed all my food shopping (at the Co-op - the only supermarket on the island) and labelled as ‘Alan’s Food Shop’ on every transaction has magically been changed to Co-op Petrol and reclassified as transport!
Some learning …