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CitiBank credit cards have several credit card offers for different types of credit histories. You may have received an invitation to apply for one of their cards at apply.citicards.com with a mail offer or by an ad.
To apply, follow these instructions or choose a different Citi credit card.
Visit apply.citicards.com and enter your 4 digit offer code.
You will then be presented with the card details and application. Fill out the application, agree to the terms of the offer and submit.
If you are approved, you should receive your new card in about a week.