There is an entire crowd source science around how to churn and different companies have different policies.

For instance signing up for business cards using your SSN as the EIN doesn’t show up on your credit report.

Once you have one card from Amex, they don’t do a credit pull for additional cards. Between personal and business, Amex has six Delta cards and four versions of the Platinum.

That means you can apply for as many Amex business cards as you want with no effect on your credit.

Chase has a hard 5/24 rule where you can’t have opened more than 5 cards with any issuer within 24 months. But that doesn’t include business cards.

You also have to space credit card applications out. It also helps that I have a long credit history. I opened my first card in 1996.

> Chase has a hard 5/24 rule where you can’t have opened more than 5 cards with any issuer within 24 months. But that doesn’t include business cards.

I've never been able to get a Chase card.

> You also have to space credit card applications out. It also helps that I have a long credit history. I opened my first card in 1996.

I think I applied for too many at once. Also I take advantage of those 0% introductory APRs and run a balance (only paying the monthly minimum for the duration, and paying the remainder as one lump sum before it expires), which adversely affects my score.

Banks seem to be OK giving cards to known churners. It should be trivial to figure out. My theory is it's either because the marketing department is happy to show off the success of their campaign, or that the banks are leveraging the high credit scores of churners to reduce the risk on-paper of customers with lower credit scores.

There are various rules that the companies use.

Sone companies like Amex have a “once per lifetime rule” and others make you wait four years and others don’t give you sign up bonuses for the same “family” of cards.

Marriott for instance has restrictions between Chase and Amex cobranded cards.

Banks still occasionally shutdown customers who follow the rules but are grossly unprofitable.

My point is, I think the banks actually want churners for the reasons I mentioned.

Banks have methods to try to limit churning some are explicit like Amex “once per lifetime rule” where you can only get a sign up bonus for a particular card once.

And they have what is colloquially known as “pop up jail” where when you try to sign up for a new card, they will allow you but pop up a warning saying you won’t get the bonus if you apply for the card. It’s based on your previous behavior with them.

But even while the algorithm for how they choose it is secret, it’s been reverse engineered for the most part via crowd sourcing.

Most credit cards also will deny you if you have opened too many recent cards no matter what your credit is. For instance I just got denied the CapitalOne SavorOne card that had 10% cash back for Uber and I have an 800+ Fico.