# Dental coordination of benefits calculator > Estimate primary payment, secondary payment, patient portion, deductibles, annual maximum impact, and non-duplication scenarios for dental claims. URL: https://dentovio.com/tools/dental-coordination-of-benefits-calculator Last verified: 2026-07-09 Billing estimate only; not a coverage determination, legal advice, clinical advice, or financial advice. Plan documents, EOBs, and applicable law control. ## Direct answer - In traditional COB, the secondary plan can pay up to the remaining allowed balance, capped by its normal benefit and remaining annual maximum. - In non-duplication COB, the secondary plan pays only the excess of its normal benefit over what the primary already paid. - A secondary plan can estimate $0 when non-duplication applies, the annual maximum is exhausted, the procedure is not covered, or plan limits block payment. ## Frequently asked questions ### How does dual dental insurance coordination of benefits work? When a patient has two dental plans, one plan is primary and pays first under its own contract. The secondary plan then coordinates against the remaining allowed balance. Traditional COB can bring the total payment up to the allowed charge, while non-duplication reduces the secondary estimate by what the primary already paid. ### What should insurance staff verify before quoting the patient portion? Verify the primary plan, the secondary plan's coordination method, each plan's allowed amount or fee schedule, deductibles, annual maximum remaining, frequency limits, waiting periods, alternate benefits, and any documentation or prior-authorization requirement. The calculator is only as reliable as those inputs. ### Which plan is primary when a child has two dental plans? For a dependent child covered by both parents, the birthday rule applies: the plan of the parent whose birthday (month and day, not year) falls earlier in the calendar year is primary. A divorce decree or custody order overrides the birthday rule. Use the birthday-rule tool to check a specific case. ### Why can the secondary dental plan pay $0? A secondary plan can estimate $0 when a non-duplication or carve-out rule applies, when the secondary annual maximum is exhausted, when the procedure is not covered by the secondary plan, or when frequency, waiting-period, alternate-benefit, or documentation rules block payment. ## Sources - `CA-HSC-1374.19` California Health & Safety Code section 1374.19. California COB rule for health care service plans covering dental services. - `CA-INS-10120.2` California Insurance Code section 10120.2. Parallel California COB rule for disability insurers issuing dental insurance policies. - `ADA-COB` ADA Guidance on Coordination of Benefits. Definitions and practice guidance for traditional COB, maintenance of benefits, and nonduplication. - `NAIC-MO-120` NAIC Coordination of Benefits Model Regulation. Common order-of-benefit rules, including birthday-rule and court-decree sequencing. - `DOL-ERISA` U.S. Department of Labor ERISA overview. Federal framework for private employer health plans; plan documents still control self-funded cases. - `CDA-COB` CDA Practice Support COB answers. California dental-practice support perspective on patient balances after both plans pay. ## Related - [Dental insurance birthday rule](https://dentovio.com/tools/dental-insurance-birthday-rule/index.html.md) - [Free dental tools and calculators](https://dentovio.com/tools/index.html.md)