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I am interested in the possible use of the Bitcoin (or other altcoin) blockchain as a generalized distributed ledger, meaning that it is useful for tracking information other than coin transactions proper. A prerequisite for that would seem to be the ability to pay for transactions whose primary purpose is not moving Bitcoins from one address to another. So, can Bitcoin transactions list no outputs, thus leaving all inputs as a transaction fee reward for the miner?

Josh Hansen
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1 Answers1

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No. If you create one, it won't be relayed or mined by Bitcoin Core. If it gets into a block, it will be rejected. From the source code for Bitcoin Core (tx_verify.cpp:164):

if (tx.vout.empty())
    return state.DoS(10, false, REJECT_INVALID, "bad-txns-vout-empty");

However, you can create a vout with 0 satoshis. That isn't a "standard" transaction, so it will not be mined by the software by default. However, if it gets into a block, it's valid.

There is another way you could do it. Using the OP_RETURN opcode. OP_RETURN in a transaction output forces anyone referencing that output to fail spending it(the script returns and transaction is invalid). Although the output exists, it is provably unspendable.

Pranay Reddy
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Nick ODell
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  • However if a custom miner puts a 100% transaction fee TX into a block, it would be accepted, and new blocks built on top of it. – makerofthings7 Aug 01 '13 at 05:19
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    @makerofthings7 That is not correct. It is a hard network rule that transactions have at least one input and at least one output. Putting a transaction without outputs in a block would make that block invalid. However, referring to the advice above, you can indeed have outputs with 0 satoshi. The network will not relay such transactions either, but they are valid inside blocks. – Pieter Wuille Aug 01 '13 at 11:33
  • I just looked through tx_verify.cpp to find a rule which would reject any vout value of 0, but couldn't find any. Can anyone point to where Bitcoin Core would reject such a transaction? – Jacob Ford May 30 '18 at 19:31