references/audit-evidence-model.md

# E-billing audit evidence model

## Governing-source priority

Use this order only when the documents expressly address the same issue: client matter-specific written instruction; executed engagement letter or approved fee amendment; client outside counsel or billing guideline; approved budget amendment; approved staffing plan; invoice data; historical billing treatment. If documents at the same priority conflict, do not choose one—flag the conflict.

## Minimum fields by check

| Check | Minimum evidence for automatic edit |
| --- | --- |
| Rate | Timekeeper identity, service date, invoice rate, authoritative rate schedule or fee term |
| Discount or AFA | Invoice basis plus expressed percentage, fixed amount, or formula and effective date |
| Time increment | Entry duration and exact rounding rule |
| Expense cap | Expense amount, category, quantity where applicable, and stated cap or formula |
| Duplicate | Two records that match on the client-defined duplicate keys or are expressly identified as duplicates |
| UTBMS code | Required code list/rule and a direct source identifying the required replacement code |
| Budget impact | Approved budget or amendment, prior approved spend, invoice total, and stated threshold rule |
| Staffing | Timekeeper identity/role, staffing restriction, and the work-date applicability |

## Never infer

Never infer whether work occurred, whether time was reasonable, whether a vague expense was necessary, whether a block-billed entry should be divided, whether approval was obtained, whether a matter is closed, or which of several codes best fits a narrative. These require explicit evidence or are flagged for review.