Coming back to this and honestly everyone is right... Amazon just isnt built for the roommate economy yet. Over the years I've tried many ways to manage this without losing my mind or my money. Basically, you have two real choices:

• The manual way: Use Splitwise. Its boring but reliable for tracking who owes what for the air fryer vs the cleaning stuff.
• The link way: Use a tool like Cart To Link. I use this for my group orders and it works great for generating those cart links instantly so everyone sees exactly what to buy. In my experience, trying to juggle four cards on one account is just asking for a locked account or someone accidentally spending on the wrong card. Just have everyone add items from a shared link to their own separate accounts. TL;DR: Amazon wont split it for you natively. Either use a spreadsheet or use Cart To Link to share the specific cart items so everyone just buys their own share separately. It is way safer.

Honestly, Amazon is pretty rigid with their payment gateway architecture. They basically force a single-payer model for security and processing efficiency. I would suggest you be careful about trying to find a native setting for this because it just isnt there for four separate debit cards. You might want to consider the risk of using one person's account for everyone's data since it can clutter up order history and tax records. I have a few questions to narrow down the best technical solution for you guys:

• Are you trying to find a tool that handles the actual multi-card transaction in one click?
• Or is the main goal just to avoid the manual entry of everyone's items into separate carts? Dealing with spreadsheets and tax math is a nightmare. Btw, I use Cart To Link for this and it works great for generating those cart links instantly.

Commenting to find later

Helpful thread 👍

Adding my two cents here because I went through this exact headache when I lived with three guys a few years back. We thought we were being smart by all logging into one account, but I would suggest being very careful with that.

• My roommate tried to add his debit card to my prime account and it triggered a huge security flag.
• They actually locked my whole account because it looked like identity theft with four different billing names on one login.
• We ended up having to call customer service for hours just to prove we lived together.
• Even if you get the cards added, the checkout process will only let you pick one primary payment method for the whole cart. Honestly, having one person be the designated buyer is usually safer, though it sucks. I learned the hard way that trying to bypass their one-card rule just causes more stress... maybe just keep a log on the fridge because tracking digital receipts gets messy fast.