I know there’s been quite a bit of debate, and confusion about this subject on this forum, going back years. After my own experiences, I decided to dig deeper, and reach out to FICO for an answer. Inquiring whether or not I might have tripped the “abuse algorithm” being my AU accounts belonging to my DW, in which we have different last names (but the same address). I’ve gotten several answers but this is the straightest answer I’ve received to date from FICO regarding AU accounts, the usage of the data provided by the CRAs, and their scoring of such.
‘Authorized user accounts aren’t considered in the calculation of this attribute of the length of credit history. FICO still considers/includes authorized users in its scoring, but doesn’t use the authorized user balance or credit limit for calculating utilization’.
So basically, yes they include the authorized user in its scoring. However, not the age of the account, or the balance of the account, or the credit limit of the account. So, in summary, all you’re getting is a positive account tallied in the overall number of trade lines you have, period.
How much that single attribute helps your particular score, and CR, who knows? Perhaps if an AU only has 1 or 2 personal accounts it has a greater effect. As your number of accounts increases, the effect on your score greatly diminishes. Speaking only to my own experience, my two AU accounts are in fact fully reported to EX, TU and EQ since they were added, and I have received zero, noticeable benefits from them but as a disclaimer, I will say, maybe YEMV.
Piggybacking on a primary's account yes you get the age metrics. No matter who charges on the card. Both will get the same usage results. On apps with some lenders they ignore the AU account. This is from EX from last June i posted.
"Since you are not responsible for the debt, the account will not appear on your Experian credit report if there is negative information in the payment history, such as late payments. However, your credit score could be hurt if the account carries a high balance because it will increase your credit utilization rate, which affects credit scores."
https://www.experian.com/blogs/ask-experian/authorized-user-accounts-can-factor-in-to-credit-scores/
Because not all credit card companies choose to report their accounts to the authorized user's credit history, you should contact the lender to make sure they report authorized-user accounts to the 3 CRA's before making the decision to add your name for the purpose of building credit. Each CRA acts a bit different.
@JoeRockhead wrote:I know there’s been quite a bit of debate, and confusion about this subject on this forum, going back years. After my own experiences, I decided to dig deeper, and reach out to FICO for an answer. Inquiring whether or not I might have tripped the “abuse algorithm” being my AU accounts belonging to my DW, in which we have different last names (but the same address). I’ve gotten several answers but this is the straightest answer I’ve received to date from FICO regarding AU accounts, the usage of the data provided by the CRAs, and their scoring of such.
‘Authorized user accounts aren’t considered in the calculation of this attribute of the length of credit history. FICO still considers/includes authorized users in its scoring, but doesn’t use the authorized user balance or credit limit for calculating utilization’.
So basically, yes they include the authorized user in its scoring. However, not the age of the account, or the balance of the account, or the credit limit of the account. So, in summary, all you’re getting is a positive account tallied in the overall number of trade lines you have, period.
How much that single attribute helps your particular score, and CR, who knows? Perhaps if an AU only has 1 or 2 personal accounts it has a greater effect. As your number of accounts increases, the effect on your score greatly diminishes. Speaking only to my own experience, my two AU accounts are in fact fully reported to EX, TU and EQ since they were added, and I have received zero, noticeable benefits from them but as a disclaimer, I will say, maybe YEMV.
Those of us who have done extensive testing (that extensive is not an exaggeration) have "proofs" that whatever is in that response, isn't the whole truth. That's totally understandable, it's not like they will publish secret sauce and continue calling it "proprietary algorithm"
I tested AAoA twice by removing AU account after it reached 2.5 and 3.5 years. All gains that materialized on the 1st of the month were lost the moment AU was removed and AAoA dropped below those thresholds. All came back when AU accounts were added again.
I no longer have any, so no more testing for me, but there are threads somewhere.
Also others did even more testing, so just do some research if this topic is of the interest to you.
If they wanted to be really nice, they should have mentioned the penalty on EX and TU (but not on EQ) when all AU accounts report $0.00
Before applying for her first card, my daughter's score was a few points below 800, solely based on AU accounts..You cannot get to 800 simply by having accounts but 0 for age. She had no loans, no other accounts in her name, just three AU cards.
@Remedios appreciate the response, and your own DPs and as I stated, YEMV because you hit the nail on the head when you said "it's not like they will publish secret sauce and continue calling it "proprietary algorithm".
I have no further interest in this subject as it is truly maddening. As a matter of fact, going forward, if you catch me participating in said topic, you have my full permission to release the wrath of Satan's Puppy on my backside. 
@JoeRockhead wrote:@Remedios appreciate the response, and your own DPs and as I stated, YEMV because you hit the nail on the head when you said "it's not like they will publish secret sauce and continue calling it "proprietary algorithm".
I have no further interest in this subject as it is truly maddening. As a matter of fact, going forward, if you catch me participating in said topic, you have my full permission to release the wrath of Satan's Puppy on my backside.
My friend, I like you too much to release Satan's Puppy.
Can we just settle on Kraken or Chupacabra?
@Remedios wrote:
@JoeRockhead wrote:@Remedios appreciate the response, and your own DPs and as I stated, YEMV because you hit the nail on the head when you said "it's not like they will publish secret sauce and continue calling it "proprietary algorithm".
I have no further interest in this subject as it is truly maddening. As a matter of fact, going forward, if you catch me participating in said topic, you have my full permission to release the wrath of Satan's Puppy on my backside.
My friend, I like you too much to release Satan's Puppy.
Can we just settle on Kraken or Chupacabra?
Well, I'll just have to take your word on that and leave it to your discretion, and fully accept the consequences. But, pretty sure I could take the chupacabra though. 
@Remedios wrote:
@JoeRockhead wrote:I know there’s been quite a bit of debate, and confusion about this subject on this forum, going back years. After my own experiences, I decided to dig deeper, and reach out to FICO for an answer. Inquiring whether or not I might have tripped the “abuse algorithm” being my AU accounts belonging to my DW, in which we have different last names (but the same address). I’ve gotten several answers but this is the straightest answer I’ve received to date from FICO regarding AU accounts, the usage of the data provided by the CRAs, and their scoring of such.
‘Authorized user accounts aren’t considered in the calculation of this attribute of the length of credit history. FICO still considers/includes authorized users in its scoring, but doesn’t use the authorized user balance or credit limit for calculating utilization’.
So basically, yes they include the authorized user in its scoring. However, not the age of the account, or the balance of the account, or the credit limit of the account. So, in summary, all you’re getting is a positive account tallied in the overall number of trade lines you have, period.
How much that single attribute helps your particular score, and CR, who knows? Perhaps if an AU only has 1 or 2 personal accounts it has a greater effect. As your number of accounts increases, the effect on your score greatly diminishes. Speaking only to my own experience, my two AU accounts are in fact fully reported to EX, TU and EQ since they were added, and I have received zero, noticeable benefits from them but as a disclaimer, I will say, maybe YEMV.
Those of us who have done extensive testing (that extensive is not an exaggeration) have "proofs" that whatever is in that response, isn't the whole truth. That's totally understandable, it's not like they will publish secret sauce and continue calling it "proprietary algorithm"
I tested AAoA twice by removing AU account after it reached 2.5 and 3.5 years. All gains that materialized on the 1st of the month were lost the moment AU was removed and AAoA dropped below those thresholds. All came back when AU accounts were added again.
I no longer have any, so no more testing for me, but there are threads somewhere.
Also others did even more testing, so just do some research if this topic is of the interest to you.
If they wanted to be really nice, they should have mentioned the penalty on EX and TU (but not on EQ) when all AU accounts report $0.00
Before applying for her first card, my daughter's score was a few points below 800, solely based on AU accounts..You cannot get to 800 simply by having accounts but 0 for age. She had no loans, no other accounts in her name, just three AU cards.
Agreed.
