I visited Aldi and Amazon's cashierless grocery stores and both overcharged me. That aside, the Amazon experience felt smoother.

Grace Dean/Insider

Grocers are testing out cashierless stores in more locations to cut costs. These stores use cameras and sensors to bill customers for what they pick up from the shelves.

Amazon opened its first cashierless store in Europe in March of 2021. The store, which uses Amazon's "Just Walk Out" technology, is known as Amazon Go in the US, but in the UK it's called Amazon Fresh.

I visited the Amazon Fresh store in Canary Wharf, which opened in May 2021.

I compared it to the only cashierless store in London. The German discount retailer opened a store in January of 2022.

Grace Dean/Insider

You have to be 18 or over to buy alcohol in the UK, but most retailers will ask for ID if you are under 25.

Alcohol was available in a small room at the back of the store. A member of staff stood at the entrance and only let people in if they were over the age of 25. This was the only part of the store where I did not see any Amazon products.

Alcohol was stacked at the end of an aisle in the store. There was a sign that said you had to verify your age using the app or a store worker.

On my first visit, I walked out of the store with alcohol, despite not seeing the sign. When I opened the app again, I saw a message saying that I needed to have my age verified, but I didn't see it on my phone.

I was able to purchase alcohol without my age being verified.

I tried using the age-verification software on the app, which requires you to take a photo of yourself, but it didn't work.

I tried to use the age-verification software in the store, but it didn't work. A member of staff told customers the store was having problems with the software.

A member of staff was near the exit gates asking customers if they had alcohol in their bag. The employee asked for my identification after I said yes.

Insider flagged the alcohol sales issues to the company, but they did not comment directly on them.

Amazon's verification system required a staff member to constantly stand next to the alcohol section. I put down to teething problems at a new store the fact that it seemed much more reliable than the age-verification system.

It was risky to rely on customers to be honest about alcohol in their bags.

Grace Dean/Insider

Both stores were able to identify nearly all my purchases.

I picked up a tin of sweetcorn at the store and put it down on my second trip, even though my receipt said it was for my first trip.

Amazon charged me for three items, but I decided not to buy them and put them back.

An Amazon spokesman told Insider that Just Walk Out technology is highly accurate.

I didn't know I was being charged for items I didn't see in my virtual basket until I left the store.

Grace Dean/Insider

The email receipt from the store had information on how to return items, but not on how to get a refund. The app receipt had a button on it that said "Do you need to change anything?", where you could say why you wanted a refund.

I applied for a refund of the sweetcorn, and I checked my app around two and a half hours later, and it said that the receipt had added a new one with all the same items. I was surprised that this was listed as a new transaction, rather than the existing one being amended.

I was able to get a refund from Amazon. I got an email the next day saying the refund had been approved, and I was able to request it quickly. The receipt was changed to include a refund.

Grace Dean/Insider

I put the teething problems at the first cashierless store of the company as the reason for Amazon's store being more efficient.

The store uses the very latest in retail technology, offering the award-winning products and unbeatable prices to customers in a new and innovative way.

I don't plan on leaving my way to return to either store. I don't have enough memory on my phone to keep the apps, so I have to closely monitor receipts after each visit.

I can see myself not making cashierless grocery shopping part of my daily routine.

Keep reading.