ACA Reporting Data Inventory: Map Your Source Systems

Begin with the questions the preparer must answer. Who was employed by which entity? What employment and eligibility history is available? What coverage was offered? Which offer terms applied in each period? Where is actual enrollment recorded? What supports the employer-level summary?

Translate each question into a data set with an owner and historical date range. A system described as “our HR source” may reliably store addresses but overwrite prior employment status. That difference determines whether an export is usable for an annual return.

Keep offer records and enrollment records separate. The IRS employer reporting Q&A distinguishes the coverage offered from whether an employee enrolled. A waived election does not erase an offer. Your inventory should preserve both facts instead of letting one overwrite the other.

For every row, add the named owner, export frequency, earliest available history, field definitions, internal identifiers, and access restrictions. Record the delivery location as a controlled reference rather than inserting passwords or credentials in the inventory.

Specify whether each file describes a point in time, a transaction history, or a period of coverage. An export dated January 10 can still describe December activity. Keep the extraction timestamp separate from the effective start and end dates of the underlying facts.

Use an internal person key to connect systems where possible, plus an employer key for entity assignment. Document how the preparer handles changed employee IDs after a rehire or conversion. Matching names alone is unsafe because names can change or collide. Preserve the source IDs in a crosswalk so a reviewer can trace a discrepancy back to its origin.

Define blank values explicitly: unknown, not applicable, and intentionally omitted should not all look identical during intake. Keep dates in a stated format and record whether an end date is inclusive. An unstated date convention can create an apparent one-day coverage gap that is only a file interpretation problem.

Assign authority by fact rather than declaring one system universally correct. Finance may establish the employer's legal name; HR may establish employment events; benefits may establish an approved plan effective date. The vendor's transformed file is an output that must be traceable to those decisions.

Write an escalation rule for each recurring conflict. For example, a termination-date disagreement goes to HR and payroll together, while a retroactive enrollment change goes to benefits with the administrator's transaction reference. Preserve both original values until a reviewer resolves the issue.

A useful resolution records the source considered, selected value, affected date range, reviewer, and reason. Avoid simply editing a cell in the final export. Without a source-level fix or documented override, the next scheduled file can reintroduce the rejected value.

Fictional Lake Elm Manufacturing changes benefits administrators on July 1. The new system provides July through December history for 146 employees, while the old system supplies January through June history for 139. The counts differ because nine people joined and two departed during the transition; 139 + 9 - 2 = 146.

The inventory marks both administrators as required sources and records the date boundary. It also identifies HR as the source for explaining the nine additions and two departures. The filing team does not assume that the new platform's “annual” export includes the old platform's history.

One employee's July record reflects an August retroactive update. The team retains the original extract and the update reference, then asks benefits to confirm the effective period. The resolution is attached to the person's internal key. All numbers and organizations in this example are fictional; the count bridge illustrates a data check, not a reporting-population determination.

Ask each owner to deliver a small sample with representative history: a stable record, a midyear change, a rehire, and a retroactive correction if those events occur in your workforce. Confirm that the preparer can read the files, connect identifiers, and distinguish current values from historical values.

Measure completion by source and period. A received file can still fail completeness if it lacks a month, excludes inactive employees, or omits a conditional data family. Record those findings in the inventory before requesting the full export.

Review the map whenever the organization changes payroll providers, plan funding, administrators, or legal entities. Use the downloadable worksheet as a maintained register. The best next step is to fill one row for the source you trust least and have its owner demonstrate how a past record can be reconstructed.