According to miles per day, Discover may also send Form 4506-C to request access to your tax return and income information. The trigger may have been a large purchase on a Discover card that had not been used for a long time: $7,500 charged on a card with an $8,000 credit limit. If you do not want this kind of financial review, it is best to avoid situations like this. Also, based on the comments there, some people provided the requested tax forms and still had their cards shut down.
We checked our own site and found a related data point as well:
Previously, AMEX was well known for using 4506-C. It could be triggered by a financial review, or when applying for a credit card with a very new credit history. If you do not provide it, there is also a chance of being denied outright. That said, 4506-C itself is a review banks use to verify whether you have the ability to repay. It mainly becomes troublesome for people who inflated their income, or who generated spending patterns that do not match their reported income.
