How do I merge neurons on the NNS dapp?

If several of your neurons have a similar dissolve delay, merging them into a single neuron makes managing them easier and allows for the more frequent merging of maturity. Merging a neuron with no dissolve delay to another neuron has the same effect as “topping up” (also known as refreshing). This article will refer to merging a "source" neuron into a "target" neuron.

In order to merge two neurons:

• The user must own both neurons — that is, they must both be controlled by the same principal id
• They must be different neurons
• Neither neuron may be involved in a current proposal, whether as a proposer or as the subject of a ManageNeuron proposal
• The ManageNeuron followees of both neurons must match
• They must agree in their KYC and not-for-profit flags, if either of these are set
• Neither neuron may be committed to the community fund, as this is not yet supported

On the Neurons page of the NNS dapp, all your active neurons are listed. On the bottom of the page, you can see a button labeled "Merge Neurons"

After clicking on Merge Neurons, a pop up window will allow you to select the two neurons you would like to merge.

After selecting the two neurons you'd like to merge, click "Merge Neurons" then "Confirm Merge"

You should now see your newly merged Neuron within the Neurons tab of the NNS.

Once the two neurons have been merged, there are quite a few things to note:

1. The entire stake from the source neuron is moved into the target neuron, minus the usual transaction fee. Any stake reserved to potentially pay rejected proposal fees in the source neuron are immediately burned.
2. All maturity in the source neuron is moved to the target neuron. Note: Since maturity is displayed as a percentage of stake in the NNS dapp, it may not be clear that this is what happened.
3. Any age accumulated in the source neuron — due to it being non-dissolving — is “moved” into the target, but only if the target is not dissolving. If the target is dissolving, any age from the source will be lost. The resulting dissolve delay will be the greater of the two neurons, which means that if you merge an 8-year neuron into a 1-year neuron, the target neuron will now have a dissolve delay of 8 years. The target neuron’s age will include any age that had accumulated in the source. This is not the sum exactly, but rather:
   ((target_stake * target_age) + (source_stake * source_age)) / (target_stake + source_stake)
4. Whether the source or the target is currently dissolving remains unchanged. So although the dissolve delay of the target is set to the larger of the two, its dissolve state is otherwise unaffected.
5. In the days following merging from a source neuron, it’s possible there will still be proposals open showing voting activity by that neuron. This means you may receive voting rewards in the form of maturity for that neuron over the next several days. This should be resolved within a week