When you create a Monero (XMR) deposit address under your Kraken account you are generating what’s called an Integrated Address.
This Monero Integrated Address contains a Payment ID encrypted within itself, which is used to determine what account a given transaction should be sent to. This extra piece of information must be included when sending a Monero transaction to your Kraken account.
Most Monero wallets support integrated address, so there should be no need to remove or alter the integrated address when sending an XMR deposit.
Leaving out the Monero Payment ID will lead to significant delays in crediting the transaction to your account, and can be irretrievable in certain cases.