How we check the math
Verification log
Every formula is worked by hand against the official rule before it ships. This page shows the source, the expected result, the result the code produced, and the date checked.
Last updated
The log is a working record, not a claim that an agency has approved the site. Where an agency publishes a worked example, the entry follows it. Where no official worked example exists, the entry says so and shows the hand calculation from the published table or rule.
The current data year is 2026. Every entry below was last checked on . The methodology page explains the boundary tests and known limits.
What is in each entry
- The formula name used in the code.
- The official source and any supporting source used for the rule.
- At least two hand-worked examples with the inputs, the arithmetic, and the expected result.
- The result the code actually produced.
- The date the example was checked.
Employer coverage affordability
Formula: employerAffordability
Primary source: IRS Revenue Procedure 2025-25. Checked on .
Supporting sources: IRS premium tax credit questions and answers; Treasury family coverage affordability rule.
The employee is tested with the lowest-cost self-only premium. A spouse and children are tested with the employee’s required family premium.
| Example | Inputs | Hand check | Expected | Actual |
|---|---|---|---|---|
| Below the line | Household income $30,000; employee-only premium $200 a month. | $200 × 12 = $2,400. The affordability threshold is $30,000 × 9.96% = $2,988. The premium is $588 below the line. | Affordable, with $588 of headroom. | Affordable: yes. Annual premium: $2,400. Threshold: $2,988. Headroom: $588. |
| Just above the line | Household income $30,000; employee-only premium $249.01 a month. | $249.01 × 12 = $2,988.12. That is $0.12 above the $2,988 threshold. | Not affordable, with a $0.12 shortfall. | Affordable: no. Annual premium: $2,988.12. Threshold: $2,988. Headroom: −$0.12. |
| Family premium test | Household income $30,000; employee-only premium $200 a month; family premium $600 a month; minimum value met. | The employee-only annual premium is $2,400, below $2,988. The family annual premium is $7,200, above the same line. | Employee coverage is affordable; family members may qualify for Marketplace help. | Employee: affordable. Family: not affordable. Family help signal: likely qualify. |
Medicare Savings Program and Extra Help
Formula: mspEligibility
Primary source: Medicare.gov Medicare Savings Programs. Checked on .
Supporting sources: CMS 2026 Extra Help resource limits; California DHCS Medicare Savings Programs; New York Medicare Savings Program; Arizona AHCCCS eligibility requirements.
Federal limits are used for launch states without a verified state override. California, New York, and Arizona use their published state figures. State disregards are not fully modeled.
| Example | Inputs | Hand check | Expected | Actual |
|---|---|---|---|---|
| Texas at the QMB line | Texas; one person; $1,350 monthly income; $9,950 countable assets. | The QMB monthly limit is $1,350 and the QMB resource limit is $9,950. Annual income is $16,200, below the Extra Help limit. | QMB likely and Extra Help likely. | QMB eligible. Extra Help eligible. Estimated monthly value: $241.89. |
| Texas above the QI line | Texas; one person; $1,817 monthly income; $0 countable assets. | $1,817 is above the $1,816 QI monthly limit. Annual income is $21,804, below the $23,940 Extra Help limit. | Extra Help only, with an apply-anyway message. | Extra Help only. Estimated monthly value: $38.99. Apply anyway: yes. |
| California resource test | California; one person; $1,330 monthly income; $130,000 countable assets. | The California QMB limit is $1,330 a month and the resource limit is $130,000 from January 1, 2026. | QMB eligible at both limits. | QMB eligible. Resource limit: $130,000. Asset test applied: yes. |
| New York without an asset test | New York; one person; $1,856 monthly income; $500,000 countable assets. | New York publishes a $1,856 monthly QMB limit and does not apply a resource test for this program. | QMB eligible despite the high assets. | QMB eligible. SLMB not separate. Asset test applied: no. |
| Arizona at the SLMB line | Arizona; one person; $1,596 monthly income; $500,000 countable assets. | Arizona publishes $1,596 as the top of the SLMB band and $1,796 as the top of the QI band for one person, with no listed resource test. | SLMB eligible at $1,596; QI eligible at $1,796. | SLMB eligible at $1,596. At $1,597, QI eligible. Asset test applied: no. |
Part B late enrollment penalty
Formula: partBPenaltyCalculator
Primary source: Medicare.gov avoid late enrollment penalties. Checked on .
Supporting sources: CMS 2026 Part B premium fact sheet.
Only full 12-month periods count. Creditable coverage is not counted when the user reports it and does not report that the Special Enrollment Period has ended.
| Example | Inputs | Hand check | Expected | Actual |
|---|---|---|---|---|
| Two full years | 24 months without creditable coverage. | Two full 12-month periods × 10% = 20%. 20% of $202.90 = $40.58. $202.90 + $40.58 = $243.48. Medicare’s rounded example shows $243.50. | $40.58 monthly penalty; $243.48 unrounded total premium. | Penalty rate: 20%. Monthly penalty: $40.58. Total premium: $243.48. Annual penalty: $486.96. |
| One full year | 12 months without creditable coverage. | One full 12-month period × 10% = 10%. 10% of $202.90 = $20.29. Total monthly premium = $223.19. | $20.29 monthly penalty; $223.19 total premium. | Penalty rate: 10%. Monthly penalty: $20.29. Total premium: $223.19. Ten-year penalty: $2,434.80. |
| Creditable coverage reported | 12 months without Part B; creditable coverage reported; Special Enrollment Period not reported as ended. | The months covered by creditable coverage are not counted, so there are zero full 12-month penalty periods. | No penalty counted, with a warning to keep the written notice. | Months counted: 0. Monthly penalty: $0. Total premium: $202.90. |
| Creditable coverage, missed SEP | 24 months without Part B; creditable coverage reported; Special Enrollment Period reported as missed. | The coverage exception does not apply after the Special Enrollment Period is missed, so all 24 months count. Two periods × 10% = 20%. 20% of $202.90 = $40.58. | $40.58 monthly penalty; 24 months counted; 0 months excluded. | Penalty rate: 20%. Monthly penalty: $40.58. Months counted: 24. Months excluded: 0. |
IRMAA cliff checker
Formula: irmaaCalculator
Primary source: CMS 2026 Part B premium fact sheet. Checked on .
Supporting sources: SSA Extra Help and IRMAA information.
The calculator applies the two-year lookback and shows each enrolled spouse separately for a joint return.
| Example | Inputs | Hand check | Expected | Actual |
|---|---|---|---|---|
| Single filer, first tier | Single; $109,001 modified adjusted gross income from the lookback year. | The first single tier starts at $109,001. Part B becomes $284.10 and Part D adds $14.50. The monthly surcharge is $95.70, or $1,148.40 a year. Headroom to $137,001 is $28,000. | Tier 1; $95.70 monthly surcharge; $28,000 headroom. | Tier 1. Part B: $284.10. Part D: $14.50. Monthly surcharge: $95.70. Annual surcharge: $1,148.40. Headroom: $28,000. |
| Married couple, first tier | Married filing jointly; $218,001 modified adjusted gross income. | The first joint tier starts at $218,001. Each spouse may pay $284.10 for Part B and $14.50 for Part D. The household monthly surcharge is $191.40, or $2,296.80 a year. Headroom to $274,001 is $56,000. | Tier 1; $191.40 household monthly surcharge; $56,000 headroom. | Tier 1. Household Part B: $568.20. Household Part D: $29. Household monthly surcharge: $191.40. Headroom: $56,000. |
Medicare vs ACA decision
Formula: medicareVsAca
Primary source: Medicare.gov when can I sign up. Checked on .
Supporting sources: Medicare.gov who pays first; Medicare.gov avoid late enrollment penalties.
This is a decision rule, not an agency formula with a published worked example. The hand check applies the published coordination and premium rules.
| Example | Inputs | Hand check | Expected | Actual |
|---|---|---|---|---|
| Active employer coverage at 66 | Age 66; active employer coverage; 25 employees; creditable coverage; 40 work credits. | The employer has 20 or more employees, so the group plan generally pays first and Part B can usually be delayed. Premium-free Part A ends Marketplace premium tax credits. The annual standard Part B premium is $202.90 × 12 = $2,434.80. | Delay Part B; premium-free Part A; ACA subsidy ends; eight-month Special Enrollment Period warning. | Path: delay Part B. Premium-free Part A: yes. ACA subsidy: ends. Annual Part B: $2,434.80. |
| No premium-free Part A | Age 66; no current coverage; 20 work credits. | Work credits are below 40, so Part A is not premium-free. Full Part A is $565 × 12 = $6,780. Part B is $202.90 × 12 = $2,434.80. Total annual premium estimate: $9,214.80. | Compare ACA; no premium-free Part A; $9,214.80 annual Medicare premium. | Path: compare ACA. Premium-free Part A: no. Annual Part A: $6,780. Annual Part B: $2,434.80. Total: $9,214.80. |
| Reduced Part A premium | Age 66; no current coverage; 35 work credits. | 30 to 39 credits use the reduced Part A premium. Part A is $311 × 12 = $3,732. Part B is $202.90 × 12 = $2,434.80. Total annual premium estimate: $6,166.80. | Reduced Part A; $6,166.80 annual Medicare premium. | Part A status: reduced. Premium-free Part A: no. Annual Part A: $3,732. Annual total: $6,166.80. |
What this log does not prove
A hand check can show that the code follows the published rule for the example inputs. It cannot decide your own case. An agency applies your full record, current state rules, and its own verification. A result can still differ because of a fact the calculator does not ask for, a state disregard, or a rule that changed after the checked date.
Plan premiums, networks, formularies, and plan-specific cost sharing are not verified here because those figures are not in the data layer. The calculators say so where that limit matters.
Report a problem with an entry
If an entry is wrong or a source has changed, email [email protected] with the formula name, the example label, and the official source you used. The corrections page explains what happens next. The site owner usually replies in 2 to 3 business days.
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