Question about ChangeAddress during a Transaction

Developers
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1

Hello everyone.

I’ve noticed that you can set a Change Address to send back to it the difference of the transaction, in cases where this is below de minimum ADA, it burns. I understand this.

  • But what happens if I don’t set a Change Address, will all the remaining get burn?
  • Can I avoid setting a Change Address by just setting up the difference of the transaction as a new output?

To explain this last point, let’s suppose I own 10.6 ADA in 3 differents UTXO as follow. (We’ll ignore fees for the following examples)

HASH               INDEX                AMOUNT
000a                   1               2100000           
000b                   4               2750000           
000c                   3               5750000

To send 8.60 ADA to a friend I would need to combine 3 of the inputs. So taking the 3 inputs, I would need to set up the outputs as follow.

ADDRESS           AMOUNT
my_address       2000000
my_friends       8600000
  • In this way, I’m specifying on my own that I need 2 ADA back to my address by setting it up on the output of the transaction. Am I correct?

Also, I’m in the possibility of splitting those 2 ADA into 2 different outputs to separate them in my next UTxO update, like this:

ADDRESS           AMOUNT
my_address       1000000
my_address       1000000
my_friends       8600000
  • Is this valid? It might be dumb to have 2 separated 1 ADA UTxO, but it’s just to illustrate the possibility.
2

Yes - since you’re ignoring fees , that is how HD wallets work. Note that every additional UTXO will increase the size of transaction and thus, marginally increase the fee as well, but it is all valid.

3

Great!

I’m trying to implement it with multi-assets UTxO, so I also don’t want to have UTxOs with huge amount of different policies/assets in it.

So the tricky part would be to balance the amount of UTxOs of the account with the amount of multi-assets in each UTxO.

4

Would having an UTxO with a very big amount of multi-assets (Let’s suppose: +1000 different policies/assets) increase the fee of a transaction?

Or would only increase the minimum ADA of the UTxO?

5

Yes - as size of the transaction increases (ofcourse it might still be cheaper than creating X amount of transactions. Besides the increase might be nominal lovelaces per additional output)

will increase the both

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6

FYI: The table at the end of this document provides a sense of how min-ADA varies with the composition of the token bundle: Min-Ada-Value Requirement — Cardano Ledger 1.0.0 documentation

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