How do additional card owners with Amex affect credit scores?

[Airforcekid]

My parents both have blank credit reports they have always paid in cash etc just this last month they signed up for NFCU and started using a debit card (Just atm withdrawls) and for the first time started using a checking /savings accounts. I let them along with my sister become addtional card users on my american express account if they use the cards will this help their credit score go up not that they really have a use for a higher score.

[parakleet]

If they're  added as an AU, it will report as a TL on their reports. It could have a positive impact provided that it's a positive TL (no baddie, etc). And they wouldn't necessarily have to use the physical card for them to benefit as an AU. 

[Airforcekid]

It never used the wording AU but did need social security numbers etc they each have cards with different numbers as well. Also does anyone know if they will get their own statements or at least a way to tell who spent how much? We plan to pay in full every month.

[Revelate]

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@parakleet wrote:

If they're  added as an AU, it will report as a TL on their reports. It could have a positive impact provided that it's a positive TL (no baddie, etc). And they wouldn't necessarily have to use the physical card for them to benefit as an AU. 

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While this is true regarding traditional AU's; have to remember that Amex AU's (ACM's) are slightly different: they get their own seperate tradeline which is independent from the primary member's tradeline.

From the sounds of it there's likely not much if any revolving history on the parents' reports, so it would likely be a benefit, but it will be treated as a new tradeline and grow over time much like adding a new tradeline yourself.

In general ACM usage for Amex is for: future backdating target / membership establishment date for the ACM, or to provide a limited spending card for an additional person (Amex does this very, very well), which is different than the traditional AU use of adding a long positive tradeline to someone's report to try to jump start it or to provide a "joint" account without requiring the secondary cardholder to meet the underwriting requirements.