Mid Term Endorsement Proration Return Premium Calculator
Prorate actual full-term premium change over remaining civil days of half-open term, exact signed rational rounding; no 360-day convention, cancellation fee or insurer/legal return entitlement.
Description
A mid-term endorsement prorates the difference between full-term premiums over remaining civil days.
A mid-term endorsement prorates the difference between full-term premiums over remaining civil days. A half-open term excludes its end date.1
The returned values include Remaining term calendar days, Total term calendar days, Signed prorated endorsement premium minor. The How section below explains the calculation, input rules and interpretation.
When to use Mid Term Endorsement Proration Return Premium Calculator
Use Mid Term Endorsement Proration Return Premium Calculator when you need to evaluate the supplied records under the calculation and evidence rules below. No 360-day convention, cancellation fee or insurer/legal return entitlement is supplied.
Prepare the observed policy, claim or quote evidence and independently verified policy tables. Monetary fields use integer minor units in one currency: for a currency with 100 minor units per major unit, enter 12345 for 123.45. One basis point is 0.01 percentage points, so 10000 basis points represents 100%.
How to use Mid Term Endorsement Proration Return Premium Calculator and understand its results
- Prepare the observed policy, claim or quote evidence and independently verified policy tables. Monetary fields use integer minor units in one currency: for a currency with 100 minor units per major unit, enter 12345 for 123.45. One basis point is 0.01 percentage points, so 10000 basis points represents 100%.
- Enter callerPolicyStartCivilDate, callerPolicyEndExclusiveCivilDate, observedEndorsementEffectiveCivilDate, callerFullTermOldPremiumMinor, callerFullTermNewPremiumMinor using the field table and calculation rules, then run the tool.
- Read remainingTermCalendarDays, totalTermCalendarDays, signedProratedEndorsementPremiumMinor. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| callerPolicyStartCivilDate | Caller policy start civil date | string | Required |
| callerPolicyEndExclusiveCivilDate | Caller policy end exclusive civil date | string | Required |
| observedEndorsementEffectiveCivilDate | Observed endorsement effective civil date | string | Required |
| callerFullTermOldPremiumMinor | Caller full term old premium minor | number | Required |
| callerFullTermNewPremiumMinor | Caller full term new premium minor | number | Required |
Enter exact real Gregorian YYYY-MM-DD dates in 1900–2199 and integer old/new premiums 0–10¹². Require start<end and start≤effective<end. Return total and remaining calendar days and exact rational signed premium change with half ties away from zero.
signedChange=roundMinor((new−old)×remainingDays/totalDays) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| remainingTermCalendarDays | Remaining term calendar days | number |
| totalTermCalendarDays | Total term calendar days | number |
| signedProratedEndorsementPremiumMinor | Signed prorated endorsement premium minor | number |
{
"input": {
"callerPolicyStartCivilDate": "2026-01-01",
"callerPolicyEndExclusiveCivilDate": "2027-01-01",
"observedEndorsementEffectiveCivilDate": "2026-07-01",
"callerFullTermOldPremiumMinor": 36500,
"callerFullTermNewPremiumMinor": 73000
},
"output": {
"remainingTermCalendarDays": 184,
"totalTermCalendarDays": 365,
"signedProratedEndorsementPremiumMinor": 18400
}
}Limitations and assumptions
No 360-day convention, cancellation fee or insurer/legal return entitlement is supplied.
Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Extremely large text inputs are rejected. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Minimum Earned Premium Cancellation Formula Calculator: Minimum-earned cancellation retains the greater of elapsed-time premium and a caller floor. Nonrefundable fees reduce the remaining refund. For a complementary task, use Short Rate Cancellation Penalty Table Lookup: Short-rate cancellation uses a verified earned-premium schedule rather than straight elapsed-time proration. An independent fee reduces the return.
References
Similar or alternative tools
- Minimum Earned Premium Cancellation Formula Calculator
Minimum-earned cancellation retains the greater of elapsed-time premium and a caller floor. Nonrefundable fees reduce the remaining refund.
- Short Rate Cancellation Penalty Table Lookup
Short-rate cancellation uses a verified earned-premium schedule rather than straight elapsed-time proration. An independent fee reduces the return.