As of December 13, 2022, Kraken has integrated Stellar Lumen (XLM) muxed address support for both deposits and withdrawals.

In the past, a Memo was required when making a deposit or sending a withdrawal to a Stellar account in order to specify which account the funds were intended for. However, if you use the muxed address, this is no longer the case and a Memo is no longer required for either Stellar deposit addresses or Stellar withdrawal addresses.

Please note: Stellar (XLM) muxed deposit addresses start with an M instead of a G.

More information about Muxed Accounts: https://www.stellar.org/developers-blog/muxed-accounts-faq 

If you do not use the muxed address please follow the instructions below:

When you create a Stellar Lumens (XLM) deposit address under your Kraken account, a unique ‘Memo’ is also generated. This Memo is an extra piece of information that can be included when sending a Lumens transaction. 

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 Lumens deposit address:

GA5XIGA5C7QTPTWXQHY6MCJRMTRZDOSHR6EFIBNDQTCQHG262N4GGKTM

The Memo is numerical and has to be included with all XLM deposits to your Kraken account. An example Memo is:

01234567

Always ensure to include the correct Memo before sending your XLM deposit. Leaving out this information will lead to significant delays in crediting the transaction to your account, and can be irretrievable in certain cases.

If you forgot to include the memo, submit a support ticket here.