Which credit unions can this person join? One API call.
POST /v1/eligibility/search takes what you know about a consumer — ZIP, employer, school, associations, military service — and returns the credit unions they can join, the ones they could join after one small step, and the published field-of-membership rule behind each verdict.
Why this is hard, and why a spreadsheet stops working
A credit union may only serve its field of membership. That rule is set per institution and published as prose — a paragraph on a membership page, a clause in a charter document — across thousands of separate sites. There is no single registry that answers “can this person join?”, which is why most teams start by hand-maintaining a rules sheet and stop when it goes stale.
- Geography
- Community charters cover people who live, work, worship or attend school in a defined area — often a county list rather than a radius, and the four verbs are not interchangeable.
- Employer
- Single and multiple common-bond charters name employers, sometimes hundreds, sometimes under former trading names.
- Association
- Membership of an affiliated group qualifies. Many such groups are open to anyone for a small fee, which is what makes some credit unions effectively national.
- Military
- Active duty, veterans, reservists, DoD civilians and their families, each treated differently by different institutions.
- Family
- A relative’s membership is often inheritable — and the definition of "relative" varies per institution.
Person-based discovery
The main endpoint. Send what you know; every field is optional.
curl -X POST "https://api.rateapi.dev/v1/eligibility/search" \ -H "Authorization: Bearer $RATEAPI_KEY" \ -H "Content-Type: application/json" \ -d '{ "home_zip": "28202", "employer": "Atrium Health", "military_status": "veteran", "willing_to_join_association": true }'willing_to_join_association: true is the highest-leverage field. Without it, institutions reachable only via an affiliated association are held back. With it, they come back as conditionally_eligible with the step named and join_cost_usd populated — frequently a few dollars. Product-wise this is the difference between “3 credit unions near you” and a national set.The other three endpoints
Discovery is one of four questions the eligibility surface answers.
/v1/eligibility/searchThe inverse: which institutions’ membership area reaches a given county, or which are open to anyone nationwide. Geo-first surfaces and coverage maps start here.
/v1/eligibility/checkBatch verdicts against institutions you already have. Use when you hold a shortlist and need it evaluated rather than discovered.
/v1/credit-unions/:id/eligibilityThe full membership record for one institution: every published rule with its source and evidence quote. This is the endpoint to render on a profile page.
# Which credit unions' published membership area reaches this county?curl "https://api.rateapi.dev/v1/eligibility/search?state=NC&county=Mecklenburg" \ -H "Authorization: Bearer $RATEAPI_KEY" # Only the ones open to anyone, nationwide:curl "https://api.rateapi.dev/v1/eligibility/search?open_to_anyone=true" \ -H "Authorization: Bearer $RATEAPI_KEY"# Every published rule for one institution, with its evidence.curl "https://api.rateapi.dev/v1/credit-unions/charlotte%20metro%7Ccharlotte%7CNC/eligibility" \ -H "Authorization: Bearer $RATEAPI_KEY"Verdicts you get back
- eligible
- A published rule matches the facts you sent.
- conditionally_eligible
- One step away. The reason names the step; join_cost_usd carries its cost when the rule states one.
- possibly_eligible
- A rule plausibly applies but your facts do not confirm it — usually one more question to the user resolves it.
- unknown
- The institution is held, but its rules are not machine-readable yet. Never treated as ineligible.
Frequently asked
A credit union is a cooperative, so it may only serve a defined group of people — its field of membership. Federal credit unions hold one of three charter types: single common bond (one employer or association), multiple common bond (several), or community (everyone who lives, works, worships or attends school in a defined geographic area). State-chartered credit unions follow their state regulator’s equivalent. The practical consequence for software is that "can this person join?" has a different answer for every institution, and the rule is published as prose rather than as data.
Yes — POST /v1/eligibility/search. It accepts consumer attributes and returns credit unions bucketed by verdict, each with the specific rule that produced it. The alternative most teams start with is scraping membership pages and hand-maintaining a rules spreadsheet, which is where this data came from originally and why keeping it current is the hard part.
Public charter data — including NCUA records — and the institutions’ own published membership pages. Every rule carries its source and an evidence quote, so a verdict can always be traced back to the sentence that justified it.
Many credit unions are reachable by anyone willing to join an affiliated association, often for a few dollars. Send willing_to_join_association: true and those institutions come back as conditionally_eligible with the step and its cost named — join_cost_usd. That single flag typically moves more institutions into reach than any other field.
No. Membership eligibility is guidance based on public data; the final determination is made by the institution, and every response says so inline. It is also entirely separate from credit approval for a specific loan product.
A directory tells you which credit unions exist and where they are. This tells you which ones a specific person can join, and why. The difference matters as soon as you are building a product surface rather than a list page — a directory cannot rank, filter or personalise.