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It's polite to send a thank you note soon after the business or person helped you. Don't delay. Write your note and send it within a few days. Time is especially important after a job interview. Contact the interviewer to say thank you within 1 day of the interview to thank them for their time. For other services, time is not as crucial. If you forgot to send a note and a week has gone by, still send the note. People appreciate receiving thanks, even if it's late. In most cases, a typed or handwritten letter is perfect for a thank you note. Both are formal enough for business correspondence, yet more personal than an email. Choose this option unless you need the letter delivered quickly or want to send a more personal card. If you don't have excellent handwriting, opt for a typed letter. Once you print or write the letter, keep it clean and tidy until you send it. Don't let it get wrinkled or spill anything on it. If you are especially thankful for something a business has done, look for a nice thank you card. This shows that you've taken an extra step to show your thanks, and the recipient will be happy to receive it. Choose an appropriate design for the card. It should still look professional. A simple card with a small design and generic text works just fine. Greeting cards are also a good choice if you know the person you're writing to personally. If you've met or spoken to this person before and built more of a relationship, a card helps solidify that relationship. While physical letters are usually more personal, an email is your best choice for fast communication. This is especially important following job interviews. If you've just had an interview or prefer your messages delivered quickly, choose an email instead. If you do send an email, write "Thank You" followed by your name in the subject line. This way, the recipient knows you sent the email by just skimming their inbox. If you prefer sending a letter but need it delivered quickly, you could send it with overnight mail. This can be an expensive service, however.
Write and send your note as soon as possible. Send a typed or handwritten letter for normal correspondence. Get a thank you card to show more appreciation. Write an email if time is short.