Free guide. Every rule links to its source.

When Medicare billing starts

For physicians and other practitioners, Medicare sets the effective date from when you file, not when you are approved. Filing before you see Medicare patients protects that date.

Checked against each source on October 12, 2026. Rules change, so confirm with the payer or agency before you file.

The effective date

For physicians, non-physician practitioners and their organizations, the effective date of billing privileges is "the later of (i) The date of filing of a Medicare enrollment application that was subsequently approved by a Medicare contractor; or (ii) The date that the provider or supplier first began furnishing services at a new practice location."

Sources (checked Oct 12, 2026)

1. 42 CFR 424.520

The 30-day look-back

These providers "may retrospectively bill for services when the provider or supplier has met all program requirements (including State licensure requirements), and services were provided at the enrolled practice location for up to ... Thirty days prior to their effective date if circumstances precluded enrollment in advance of providing services to Medicare beneficiaries." The window is ninety days after a Presidentially declared disaster.

Sources (checked Oct 12, 2026)

1. 42 CFR 424.521

What this means in practice

• File before the first Medicare visit whenever you can; the filing date is what counts.
• Online PECOS applications "tend to process faster than paper applications," according to CMS.
• Medicare is only one payer. Medicaid and each commercial plan have their own applications and timelines.

Sources (checked Oct 12, 2026)

1. CMS: Medicare enrollment applications

More guides

• Virginia payer enrollment guide: Medicare, Virginia Medicaid and the commercial plans, in order.
• Virginia Medicaid enrollment: DMAS PRSS enrollment and the five Cardinal Care plans.
• How long credentialing takes in Virginia: Each payer's own published estimate, and Virginia's 60-day rule.
• CAQH re-attestation: Every 120 days, and why a plan may not see your profile.
• Medicare revalidation: Due dates, notices, and what happens if you miss one.
• Adding a new clinician: Medicare reassignment and each insurer's own process.
• Type 1 vs Type 2 NPI: Which NPI you need, and choosing a taxonomy code.
• Credentialing readiness checklist: What to have ready before you apply (interactive).

This page is general information, not legal advice. Rules and payer processes change; always follow the payer's or agency's current instructions. Payer, agency and product names belong to their owners and are used only to describe what each step involves.