Secondary balance after primary

Outcome

You understand how the platform computes residual balance after primary adjudication, how secondary (and tertiary) absorb the patient liability the primary surfaced, and what the patient AR looks like at each step.

Prerequisites

Scope	What it lets you do
billing.claim.read	View claim relationships
billing.cob.read	See the COB waterfall
billing.receivable.read	Watch posting effects

The waterfall

At each level, the platform computes:

residual = billed − sum(payments) − sum(contractual adjustments) − sum(prior-payer impact)

Patient AR doesn't "fill" until the chain completes for that line.

Why primary's PR-* doesn't immediately bill the patient

When a member has a secondary, the primary's PR-* is expected to move down to the secondary. The platform:

Action	When
Holds the patient AR routing	Until secondary submits / adjudicates.
Releases to patient AR	If secondary genuinely doesn't cover.
Closes the line	If secondary fully covers the residual.

Tenants without held-routing (the simpler model) post PR-* immediately and reverse later if secondary covers. Read your tenant's policy.

Reading the COB tab on a claim

/claims/:id → Relationships → COB waterfall:

Section	Contents
Primary	Adjudication summary + residual.
Secondary	If applicable; same shape.
Tertiary	If applicable; same shape.
Patient AR	Final residual, who's on the hook, what's been paid.

The shape repeats per claim line where applicable.

Working a stuck COB chain

Common patterns

Pattern	Read
Secondary built immediately, paid the residual	Standard happy path.
Secondary built, pended for medical review	Tertiary doesn't auto-trigger; track follow-up.
Secondary denied for "no primary EOB attached"	The 837 to secondary lacked the primary CAS — re-check the build.
Tertiary built unexpectedly	Member had a tertiary the COB tab missed; verify Coverage.
Patient AR shows full liability while secondary still pending	Tenant policy is "release immediately"; will reverse on secondary post.

Validation

Check	Expected
Primary post triggers secondary build (where applicable)	Yes.
Secondary 837 carries primary CAS / AMT*F2	Yes (visible on Submission tab).
Tertiary auto-triggers after secondary PAID/PARTIAL	Yes.
Patient AR equals final residual after chain completes	Yes.

Troubleshooting

Symptom	Cause	Fix
Patient is being billed for amounts secondary should cover	"Release immediately" policy; secondary hasn't paid yet	Wait for secondary 835; balance will reverse.
Secondary built with wrong primary CAS	Primary's CAS wasn't snapshotted correctly	Reverse + rebuild secondary; investigate.
COB tab shows tertiary but member has only two coverages	Stale member record	Refresh eligibility; re-snapshot COB.
Long-pended secondary	Payer's queue	Send 276 inquiry on the secondary claim.

Where to next

• 7.3 — Statements — when patient AR turns into a statement.
• 3.5 — Secondary & tertiary COB — the underlying mechanics.