The single most-misunderstood credit factor.
Most consumer credit advice optimizes for utilization (~30% of the score) and payment history (~35%). Both are correct. But AAOA — average age of accounts — is the third-largest factor at 15%, and it's the only one you can't fix in a single statement cycle. It takes years to move, which is why pre-application timing matters more here than anywhere else.
The math
AAOA is the simple arithmetic mean of every credit account's age, in months or years.
Example file:
- Capital One Visa, opened January 2018 (8 years old)
- Chase Sapphire, opened June 2020 (5 years 10 months)
- Discover It, opened March 2023 (3 years 1 month)
- Auto loan, opened August 2024 (1 year 8 months)
AAOA = (8.0 + 5.83 + 3.08 + 1.67) ÷ 4 = 4.65 years
That's a respectable mid-tier file. FICO would treat the "length of credit history" factor as solid but not maximum. Above 7 years is where it tops out for scoring purposes.
Two related metrics that often confuse people
Age of oldest account — separate from AAOA. The single oldest open account, not the average. FICO uses both: AAOA in the length factor, age of oldest in a sub-factor for "credit longevity."
Age of newest account — also separate. Affects "new credit" factor (10% of score). A file with a brand-new account is treated differently than a file with no recent openings.
So three different "age" metrics in three different score sub-factors. The pre-application implication: optimizing one doesn't optimize the others.
Why opening a new account drops your score
You have AAOA = 7 years across 5 accounts (35 years of total account history ÷ 5 = 7).
You open a new credit card. The new account is 0 days old.
New AAOA = 35 years of history ÷ 6 accounts = 5.83 years.
You just dropped your average age by ~17%. The score impact is non-trivial — typically 5-15 points on FICO, more if your file was thin to begin with.
This is the trap most pre-mortgage applicants fall into: a credit card company sends a nice 0% balance-transfer offer, the applicant takes it 4 months before their mortgage application, and they show up at the lender with a 12-point lower score than they had 4 months ago.
The defensive move: no new accounts in the 6 months before any major credit application, period. The 0% offer can wait.
Why closing an old account is dangerous (eventually)
Common myth: "closing a credit card I don't use can't hurt my score because I'm not using it anyway."
Wrong. Two effects:
Immediate: closing a card removes its limit from your aggregate utilization denominator. Same balances, smaller denominator, higher utilization. This part can hit hard immediately.
Eventual: closed accounts remain in your AAOA calculation for ~10 years (FICO 8 keeps them; some scoring versions are slightly different). At the 10-year mark they age off, and at that point your AAOA suddenly drops. If you close an old account today and then 10 years from now you also have a major application coming up, you may take a score hit you can't immediately undo.
For a deep dive on the closing-an-account decision: see Closing a credit card: when it helps your score and when it tanks it.
How to actually grow AAOA
Slowly. There's no shortcut.
The one structural lever: authorized user (AU) tradelines. If a parent or spouse adds you as an authorized user on their oldest credit card, that card's full age and history reports on your file. A 25-year-old card from your mom can move your AAOA from 4 years to 8 years overnight.
Caveats:
- Not all credit cards report AU status to the bureaus. AmEx, Chase, Discover, Capital One, BoA, Citi all do. Some smaller issuers don't.
- Some FICO versions weigh AU tradelines lower than primary tradelines (FICO 8 partially discounts them; FICO 9 weights them more equally). Mortgage-specific FICO 5/4/2 still weights them but underwriters look closely.
- AU tradelines can be removed by the primary cardholder, which removes the history from your file.
For the mechanics and version-by-version weights: see Authorized-user tradelines and FICO versions.
The other (slower) lever: don't close old accounts. Even an old store card with a $300 limit you haven't used in 8 years is contributing positively to your AAOA. If there's no annual fee, leave it open. If there is an annual fee, downgrade to a no-fee version of the same card (most issuers allow this) — that keeps the account number, the open date, and the tradeline history.
What thin-file applicants should do
Files with AAOA under 2 years are "thin" by lender standards. Mortgage underwriting in particular wants to see at least 3 active tradelines with 24+ months of history each.
If your file is thin and you have a mortgage application 12-18 months away:
- Open 1-2 credit cards now (not later — earlier is better, AAOA grows from this point)
- Use them lightly for 6+ months to establish payment history
- Stop opening any new accounts at the 6-months-before-application mark
- Use the remaining 6 months to optimize utilization
For a thin-file specific plan: see Manual underwriting: how lenders review thin credit and Credit-builder loan vs secured card.
Where Paliscore fits
The readiness check audits your AAOA against the depth your specific funding lane needs. For a mortgage, lenders generally want 5+ years AAOA with at least one tradeline at 5+ years. For SBA, they look at both personal AAOA and business credit foundation. The check identifies whether AAOA is your bottleneck and tells you whether to wait, add depth via AU, or apply now with a manual-underwriting backup plan.
Take the readiness check — 2 minutes, free.
Sources
- FICO, "What's in your FICO Scores" — myfico.com/credit-education/whats-in-your-credit-score
- Experian, "What Is Length of Credit History?" — Experian consumer education
- CFPB, "What's the difference between an authorized user and a joint account holder?" — consumerfinance.gov
- Fannie Mae Selling Guide B3-5 (Credit Assessment) — fanniemae.com