Sum of block values not zero?

Question

Take for e.g. block 163440. The amount paid out in the coinbase transaction is not reward+fees. Does the network not require blocks to have a sum of zero for all transactions + block reward? Confusingly blockchain.com reported 50 BTC to be minted. In this case this is not correct right?

Answer 1

The amount paid out in the coinbase transaction is not reward+fees.

The link you shared shows

Input Value   3,067.86 BTC  
Output Value  3,117.80 BTC 

The difference ought to be the reward claimed by the miner in the coinbase transaction, but the difference is only 49.94

It also shows

Minted 50.00 BTC  
Reward 50.05750000 BTC

So it does seem there is a discrepancy.

I compared it with https://blockchair.com/bitcoin/block/163440

Input total  3,067.86 BTC  
Fee total        0.0575 BTC  
Generation      49.94 BTC  
Output total 3,117.80BTC  

Note the difference between this explorer's Generation and blockchain.com's Minted.

It shows the output for the coinbase transaction as 50 BTC.

So I suspect the miner forgot to claim the transaction fees and only claimed the mining reward for the block.

I believe the explorers wrongly interpret this as the miner having claimed 0.0575 BTC in fees and under-claimed approximately 49.94 BTC as a mining reward for the block. Blockchain.com shows 50 as "Minted" - which is an inconsistency in its presentation. It shows the total reward that could have been claimed, not what was actually claimed.

This under-claiming of rewards is within the Bitcoin rules, the miner cannot claim more than block-reward plus transaction fees but they can claim less.

Answer 2

You’re right, the “minted” value looks misleading in this context. It seems that it actually contains the “allowed amount to be created” rather than the amount of new bitcoins that were actually created by the block.

---

Generally, the sum of output values on a transaction must be equal or smaller than the sum of input values. The difference between input values and output values is referred to as the transaction fee:

Σ(inputs) – Σ(outputs) = transaction_fee

The exception to this rule is the coinbase transaction. The coinbase transaction is the only transaction that can have a bigger output than input. It does not spend a UTXO in its input, but it may collect the mining reward in its outputs. The mining reward is composed of the block subsidy and transaction fees. The block subsidy depends on the block height and the transaction fees depend on the transactions included in the block:

reward ≤ ⌊5×10^9 × 0.5^(⌊block_height/210,000⌋)⌋ + Σ(tx_fees)

That means that generally the sum of outputs of transactions in a block will exceed its inputs by the block subsidy. However, a block is still valid if the miner collects less than the allowed amount— the unassigned rest is simply lost forever.

Beside the block that you are looking at, miners collected less than allowed on more than 1000 blocks already, see the answer on this question for a few examples: Will there be 21 million bitcoins eventually?