Don't understand fees on a particular bitcoin block

Question

I am comparing and contrasting blocks 200000 and 164246 of the bitcoin blockchain (looking via the bitcoind api or https://www.blockchain.com/explorer?utm_campaign=expnav_explorer is fine).

Looking at the coinbase transaction in 200000, the output amount (of 50.635...) is clearly the sum of the mining fee (50) and the sum of the transaction fees.

Looking at 164246, the coinbase output amount is exactly 50. Yet there are clearly fees in the 100 transactions in the block. Where have the fees gone? Have they not been collected by the miner?

Answer 1

Yes, according to the Bitcoin protocol rules, miners can claim up to the maximum block reward (subsidy + fees). This answer goes into more detail into this and other ways bitcoins can be lost.

Using a block explorer like blockchair.com you can construct a query for blocks that have non-zero fees but nevertheless have claimed exactly 50 BTC: https://blockchair.com/bitcoin/blocks?s=fee_total(desc)&q=fee_total(1..),reward(5000000000)#f=id,time,guessed_miner,fee_total,reward

As you can see it returns around 200 blocks in total. If you sort them by total fee, block 164246 is right on top, having failed to collect around 1.76 BTC in fees. You can try the same thing for other block subsidies (25, 12.5 and 6.25 BTC).

Answer 2

Bitcoin's consensus rules only stipulate that the miner can not claim more than the subsidy + fees in their coinbase transaction. There is no requirement that they clain the full amount, so it is possible for a miner to claim less than the amount that they are entitled to. The unclaimed coins are thus lost forever.

Of course it is in a miner's best interest to claim as much of the reward as they can. They are financially incentivized to do so. However there have been bugs in mining software which have resulted in several blocks failing to claim the full amount, and that has resulted in those coins being permanently burnt.