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Recently Updated NPI Information — some details in this NPI profile have been updated in the NPI registry within the last 60 days.

DR. MATTHEW CRAIG WILLIAMS MD
NPI 1326626797
Psychiatry & Neurology - Child & Adolescent Psychiatry in Mill Valley, CA

Active since March 29, 2021PECOS EnrolledAccepts Medicare Assignment
655 REDWOOD HWY FRONTAGE RD STE 261, MILL VALLEY, CA 94941(415) 381-1690 Get Directions Write a Review

NPPES record last updated: June 9, 2026. Verified against the NPPES registry weekly; last sync: August 02, 2026.

Record update history: May 2, 2024, Nov 1, 2021, Mar 29, 2021 (3 updates tracked since 2021).

About Dr. Matthew Craig Williams Md NPPES

Official registry information on file with the National Plan and Provider Enumeration System.

DR. MATTHEW CRAIG WILLIAMS MD (NPI 1326626797) is an individual child & adolescent psychiatry provider in Mill Valley, California, licensed in California (A186478) and active in the NPI registry since March 2021. He is enrolled in Medicare PECOS and is a graduate of Georgetown University School Of Medicine (2021).

NPPES Registry Identity

NPI1326626797
Entity TypeIndividualMale
Primary Taxonomy2084P0804X
Provider Legal NameDR. MATTHEW CRAIG WILLIAMSCredential: MD
Location Address655 REDWOOD HWY FRONTAGE RD STE 261Mill Valley, CA 94941-3011
Mailing Address655 Redwood Hwy Frontage Rd Ste 261Mill Valley, CA 94941-3011 · (415) 381-1690
Phone(415) 381-1690
Sole ProprietorNo
Medical School CMSGeorgetown University School Of MedicineGraduated 2021
Enumeration DateMarch 29, 2021
Last NPPES UpdateJune 9, 20263 updates tracked since enumeration
NPPES CertifiedJune 9, 2026
✔ NPI 1326626797 is a valid, active identifier and passes the ISO check-digit test.

Specialties & Licenses 2

★ Primary SpecialtyPsychiatry & Neurology · Child & Adolescent PsychiatryAllopathic & Osteopathic Physicians
Taxonomy Code2084P0804X
License✔ Licensed in CA · A186478
Definition
Child & Adolescent Psychiatry is a subspecialty of psychiatry with additional skills and training in the diagnosis and treatment of developmental, behavioral, emotional, and mental disorders of childhood and adolescence.
Also ListedPsychiatry & Neurology · PsychiatryTaxonomy 2084P0800X · License A186478 (CA)
655 REDWOOD HWY FRONTAGE RD STE 261, Mill Valley, CA 94941
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Medicare Participation & PECOS CMS

Medicare enrollment, assignment, and ordering and referring status from the CMS PECOS system.

Medicare Enrollment Status

✔

Enrolled in Medicare and accepts Medicare assignment

Dr. Matthew Craig Williams Md is registered in PECOS and agrees to accept the Medicare-approved amount as full payment. Medicare patients are not billed beyond the standard deductible and coinsurance.

PECOS PAC ID6709259203
PECOS Enrollment IDI20231109003422
Eligible to Order & Refer✔ Part B Labs & Imaging✔ Durable Medical Equipment✔ Home Health Agency✔ Power Mobility DevicesPer the CMS Ordering and Referring file. Eligibility means Medicare pays claims that this provider orders or refers for these categories.

Areas of Expertise CMS Part B claims 3

Services this provider delivered to Medicare fee-for-service patients, from the CMS Medicare utilization data. Higher counts generally reflect more experience with a service; care delivered outside Medicare is not included.

Subsequent hospital care with moderate levelof medical decision making, if using time, at least 50 minutes 99233
Follow-up hospital inpatient care per day typically involves a 35-minute check-up by your healthcare provider. This service includes monitoring your health progress, adjusting your treatment plan if needed, and answering any questions you may have about your condition or care.
80 services40 patients
Psychotherapy with evaluation and management visit, 30 minutes 90833
Psychotherapy with evaluation and management is a 30-minute session where a mental health professional talks with you about your concerns and feelings. They assess your mental health, provide support, and manage your treatment plan to help improve your well-being.
73 services40 patients
Psychiatric diagnostic evaluation with medical services 90792
A psychiatric diagnostic evaluation with medical services is a comprehensive assessment. It includes a detailed examination of your mental health and physical wellbeing, as well as your personal and family history. This evaluation aids in creating an effective treatment plan.
15 services15 patients

Other Providers at the Same Location NPPES 2

Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.

BRITTANY SMITH MD
Psychiatry & Neurology (Psychiatry)
655 REDWOOD HWY FRONTAGE RD STE 261
MILL VALLEY, CA 94941
Marin County (415) 381-1690
DR. MICHAEL RAMSEY D.O.
Psychiatry & Neurology (Child & Adolescent Psychiatry)
655 REDWOOD HWY FRONTAGE RD STE 261
MILL VALLEY, CA 94941
Marin County (415) 704-7066

Frequently Asked Questions NPPES & CMS

Common questions about this NPI record, answered from the official NPPES registry and CMS datasets shown on this page.

What is Matthew Williams's NPI number?

The NPI number for Matthew Williams is 1326626797. It was assigned to this individual provider in the NPPES registry on March 29, 2021.

Where is Matthew Williams located?

Matthew Williams practices at 655 Redwood Hwy Frontage Rd Ste 261, Mill Valley, CA 94941. The listed phone number is (415) 381-1690.

What is Matthew Williams's specialty?

The primary specialty registered for this NPI is Psychiatry & Neurology, specializing in Child & Adolescent Psychiatry, with taxonomy code 2084P0804X.

Is Matthew Williams enrolled in Medicare?

Yes. Matthew Williams is registered in the Medicare PECOS system and accepts Medicare assignment, which means accepting the Medicare-approved amount as payment in full for covered services.

When was this NPI record last updated?

The NPPES record for Matthew Williams was last updated on June 9, 2026. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 59 days ago. If this record has changed at CMS more recently, you can request an on-demand re-check against the live CMS registry, directly from this page.