When you create an EOS deposit address on your Kraken account, a unique "Memo" is also generated. This Memo is an extra piece of information that must be included when sending an EOS transaction to Kraken.
On Kraken, the Memo is used to determine what account a given transaction should be assigned and credited to. This is because all Kraken accounts use a single EOS deposit address:
krakenkraken
The Memo on Kraken is a unique numerical message and has to be included with all EOS deposits to your Kraken account. An example Memo is:
9876543210
Always ensure to include the correct Memo before sending your EOS deposit. Leaving out this information will lead to significant delays in crediting the transaction to your account and can be irretrievable in certain cases.
Note: It is not possible to transfer cryptocurrencies between two Kraken accounts. Any such transaction will result in the transaction failing with a "Failure" status.
If you forgot the memo submit a support ticket here.