I Added a 9-Year Authorized-User Tradeline 40 Days Before a Car Loan

On a Saturday in late September, the finance manager at a used-car dealership turned his monitor toward me and pointed at a three-digit number. I had checked a credit score most mornings for forty days, and I had never seen this one. The label beside it read FICO Auto Score 8, TransUnion. The number in my bank's app was a FICO Score 8 built on Experian data, so the model, the bureau and the scale were all different.

Forty days earlier my sister had added me as an authorized user on a credit card she opened in 2017. I was about to ask for a $28,000 car loan, and I had typed the question a lot of people type: can a tradeline help me get a car? A tradeline is an account as it appears on a credit report.

The documents I read get as far as this: it may help, and how much is not published anywhere. I kept a log of what I could observe: when the account reached each of my credit reports, which score the dealer pulled, and what the lender asked about that no score contains. It is one file. Results vary from one file and one lender to the next, and nothing in this one predicts yours.

Day 0 was a Monday in mid-August. My own file was thin: one credit card in my name, opened fourteen months earlier, with a $1,000 limit and no late payments. That day my sister called her card issuer and added me to an account she opened in June 2017, a little over nine years before. It carries a $12,000 limit, and her statements usually close with a few hundred dollars. I pulled my reports from all three bureaus the same day as a baseline, and a card with my name on it arrived the following week.

The published record stops there. FICO does not say how much less impact, which versions count as recent, or how the logic tells one account from another. On Day 0 all I knew was that the account could count.

My sister's statement closed on Day 11, and on Day 14 I pulled all three reports again. The account was on my Experian and TransUnion reports and not on Equifax. Day 28 and Day 39 gave the same result.

On the two reports that carried it, the entry showed her June 2017 open date, the $12,000 limit, a $480 balance, a payment history with no late marks, and a responsibility field reading authorized user.

On Day 40 I asked the finance manager which score he was looking at and from which bureau, and he read it off the screen: FICO Auto Score 8, TransUnion, 661. Two days earlier my bank's app had shown a FICO Score 8 of 672 on Experian data.

I have left my Day 0 base score out of this post. In those forty days my own card aged another month, and I paid its reported balance down from $310 to $40. myFICO says "it's not possible to measure the exact impact of a single factor" without looking at the entire report. Printed beside the Day 38 number, it would read as the tradeline's effect, and I cannot isolate that.

The score took a few seconds. The rest of the hour went to things no credit score contains: two pay stubs, my monthly rent, how long I had been at my job, how much I was putting down and how long I wanted to pay.

On who decides what counts, myFICO says: "It is up to each lender to determine which credit score they will use and what other financial information they will consider in their credit review process."

One visit produced three hard inquiries on my TransUnion report, all dated Day 40, because the dealership sent my application to three lenders. On Day 42 I applied at my credit union, which added one more.

The credit union asked the same income and down payment questions and offered 11.4 percent over 60 months on the same $28,000. I took it. The Consumer Financial Protection Bureau's page on auto loan rates says of lenders: "Keep in mind that they're not required to offer you the best rates."

If I did this again, I would treat the tradeline as one more thing to verify before the visit. In order, I would:

• Pull all three reports before applying and confirm the account is on each one, with the open date, limit and balance I expect.
• Ask the cardholder what balance their statements close with.
• Ask the lender which score and which bureau it uses.
• Bring proof of income, and work out the loan amount against the car's value before sitting down.
• Keep every loan application inside a few days.

For the longer run, myFICO says "it's also important to have credit accounts where you are the primary account holder." My fourteen-month-old card is the account that stays mine if my sister ever closes hers.

The dealer's lender happened to pull one of the two reports that carried the account. I still cannot say the account is why I was approved, or what it was worth in points. FICO does not publish what an Auto Score does with such an account beyond saying the model guards against piggybacking, and my file changed in three ways at once: the new account, another month of age on my own card, and a lower reported balance.

I could check whether the line was on the report the lender pulled and which score that lender used, and I could watch the quote move with the down payment and the term while the score sat still.

I signed the credit union's loan: $28,000 over 60 months at 11.4 percent, 2.5 percentage points under the dealer's first quote.

1. Can a tradeline help me get a car loan?

It may help, and by how much is not published. FICO says authorized-user accounts can appear on your credit report and affect your FICO Score, and that in recent versions they have less impact than accounts you own. No point value is published, and the lender decides which score to use and what else to weigh, including income, debts, down payment and term.

2. What credit score do car dealers and auto lenders use?

It is up to each lender. myFICO says FICO Auto Scores are the industry-specific scores used in the majority of auto financing-related credit evaluations, and that industry-specific versions range from 250 to 900 compared with 300 to 850 for base FICO Scores. A lender may also use a different score altogether, so ask which score and which bureau it pulled.

3. How long does an authorized-user account take to show up on a credit report?

The issuer and bureau statements cited in this post do not promise a date. Equifax says there is no set day or time when a credit card company reports, and that creditors who report should do so monthly, usually on the billing cycle date. In this log the account was on two of three reports by Day 14 and still missing from the third on Day 39. Check all three reports before you apply.

4. Does a FICO Auto Score count authorized-user accounts?

FICO has published very little on it. Its 2009 announcement of the auto version of FICO 08 says the score includes protection against authorized user account piggybacking, without saying how that works. The myFICO page that describes Auto Scores does not mention authorized users, and FICO says it does not output more information beyond the score, reason codes and exclusion codes. You can confirm whether the account is on the report the lender pulled, but not what the score did with it.

5. How long is the rate-shopping window for auto loans?

myFICO says FICO Scores group multiple hard inquiries made within a short time frame, 14 to 45 days, into one inquiry. The shopping period is any 14-day span for older versions of the formula and any 45-day span for the newest versions, and each lender chooses the version. myFICO does not list which version numbers get which window, so the 14-day span is the safer one to plan around.

6. What does an auto lender look at besides my credit score?

The Consumer Financial Protection Bureau lists your credit scores and history, your income and debts, the amount of the loan, the loan term, the down payment in relation to the value of the vehicle, and the type of vehicle. On this file, moving from $3,000 down over 72 months to $5,000 down over 60 months changed the quote from 13.9 percent to 12.6 percent while the score stayed the same.

7. Is it legal to pay for an authorized-user tradeline before a car loan?

The Federal Trade Commission's 2020 complaint against BoostMyScore says the agency has never determined that credit piggybacking is legal. Under the settlement the FTC announced with that case, the defendants would be prohibited from selling fake access to another consumer's credit as an authorized user. This post adds no verdict to the agency's statement, and the account in this log came from a family member who gave real access to the card.