---
title: IBillingDetailExtentions
summary: API reference for IBillingDetailExtentions.
status: draft
owner: Technical Writer
last_reviewed: 2026-07-31
library: SAIF.Business.Policy.Premium
reference_type: package
---

# IBillingDetailExtentions

Extension module on `IBillingDetail` (source file name is `IBillingDetailExtentions.vb` -- note the misspelling of 'Extensions' in both the type and file name); provides utility extension methods that operate on `IBillingDetail` implementors.*

## Purpose
- Extends `IBillingDetail` with utility operations for callers that work with billing detail abstractions.*
- Consumed by billing workflows that need common utility operations on billing detail objects without depending on the concrete type.*

## Context
- Namespace: `SAIF.Business.Policy.Premium`
- Assembly/package: `SAIF.Business.Policy.Premium`

## Public members
| Member | Signature | Purpose |
| --- | --- | --- |
| FirstBillDate | `Public Function FirstBillDate(Target As IEnumerable(Of IBillingDetail)) As Date` | Executes the first bill date behavior defined by this type. |
| FirstBillDateDetails | `Public Function FirstBillDateDetails(Target As IEnumerable(Of IBillingDetail)) As IEnumerable(Of IBillingDetail)` | Executes the first bill date details behavior defined by this type. |
| IsDepositOrAdvanceInstallment | `Public Function IsDepositOrAdvanceInstallment(Target As IBillingDetail) As Boolean` | Executes the is deposit or advance installment behavior defined by this type. |
| ByBillingDetailMethod | `Public Function ByBillingDetailMethod(Target As IEnumerable(Of IBillingDetail), inBillingDetailMethod As BillingDetailMethods) As IEnumerable(Of IBillingDetail)` | Executes the by billing detail method behavior defined by this type. |
| SumOfBillAmount | `Public Function SumOfBillAmount(Target As IEnumerable(Of IBillingDetail)) As Decimal` | Executes the sum of bill amount behavior defined by this type. |
## Behavioral notes
- Source file: `Business\SAIF.Business.Policy.Premium\Billing\clsBillingDetail.vb`.

## Constraints and usage notes
- The type and file name misspelling (`Extentions` vs `Extensions`) is a known quirk in the source; do not rename without coordinating with all dependents.*


> **Note:** Statements marked with * were inferred from code structure, naming conventions, or
> contextual evidence where direct confirmation was not available in source artifacts. Statements
> marked with ** could not be confirmed; treat as unknown until verified.

## Sources
- `Business\SAIF.Business.Policy.Premium\Billing\clsBillingDetail.vb`