I'm trying to send a portion of ADA but I need to confirm sending more and another address I don't recognize. Why is that?

This is because Cardano Blockchain is using the Unspent Transaction Outputs (UTxO) model. Meaning that for every transaction with a specific amount of ADA you get, Cardano will automatically categorize those ADA from that same transaction into one UTxO. This might be non-intuitive at first, but we can use the cash analogy to understand it better.

Let's say on Monday we go to the ATM to grab a $50 bill, and then on Tuesday, we go to the ATM again to get a $20, and again on Wednesday to get a $20. So now we have a total of $90 in our physical wallet, consisting of one $50 bill, and two $20 bills. When we need to pay for something that costs $60, we have to give them one $50 bill and one $20 bill - before getting $10 back after we made the payment.

So for example you’ve acquired ADA from 3 different transactions:

1. one time containing 30 ADA,
2. one time containing 20 ADA,
3. and the third one containing 50 ADA.

Now you have 100 ADA in your wallet, consisting of three UTxO:

1. one UTxO contains 30 ADA,
2. another UTxO contains 20 ADA,
3. and the third UTxO contains 50 ADA.

Same as the cash, in the case when you need to send out 90 ADA, the system will create a new address out of all three UTxOs (30 ADA + 20 ADA + 50 ADA); send it to your recipient, and you will receive 10 ADA back.

On the other hand, say you have to send out 10 ADA, the system will use one of the existing UTxO to send out 10 ADA, and you will receive the remaining back.

If you want more information regarding the UTxO model, click here.

Updated on: 14/08/2025