Children pay for their parents – What are all the rules regarding charging CPFP fees?

Unlike RBF, CPFP is not a relay policy, so there are no specific relay policy rules that apply to CPFP. This is a completely normal new additional transaction being relayed. The fee increase effect is not achieved by a special relay mechanism, but by the miner’s block-building mining logic that recognizes that a combination of parent and child is better than the parent alone.

For this to work, the block building code must be strong enough to recognize this. This applies if the miner directly or indirectly uses Bitcoin Core (version 0.13.0 or higher).

There are general policy rules that apply to dependent transactions, such as a limit on the number of parents and children, which is 25 transactions by default. Although it is not specific to CPFP, it may affect its use.