According to the text, thank-you notes for presents should be sent . the day after you received them by the middle of the next month within a week

Thank you should be sent immediately or the day after you received them.

Explanation:

Thank you should be sent immediately after you received gifts or hospitality because it is to show gratitude and delay to send or say thank you immediately is a sign of ingratitude.

Thank you is a sign of respect and it is use for expressing gratitude for things done. If we did not say thank you, our relationship might change and the person may not want to help some other time.