561621

Security Systems Services (except Locksmiths)

Administrative and Support and Waste Management and Remediation Services › Administrative and Support Services › Investigation and Security Services

SBA Size Standard

$25M average annual receipts

Revenue-Based Verify at SBA.gov →

NAICS Code Hierarchy

56

Sector

Administrative and Support and Waste Management and Remediation Services

561

Subsector

Administrative and Support Services

5616

Industry Group

Investigation and Security Services

561621

National Industry (This Code)

Security Systems Services (except Locksmiths)

Official NAICS Description

Source: U.S. Census Bureau 2022 NAICS

📘 Source: U.S. Census Bureau — 2022 NAICS Manual
This U.S. industry comprises establishments primarily engaged in (1) selling security alarm systems, such as burglar and fire alarms, along with installation, repair, or monitoring services or (2) remote monitoring of electronic security alarm systems.

✓ Small Business Eligibility at a Glance

Based on SBA Table of Small Business Size Standards (2024)

Size Standard

$25M average annual receipts

Measurement Period

3-year average

Standard Type

Revenue-Based

Applies To

All contracts under NAICS 561621

Set-Aside Programs

8(a), WOSB, HUBZone, SDVOSB

Certification Required

No (self-certify in SAM.gov)

Size standards are set by the SBA and reviewed periodically. Always verify at SBA.gov before bidding.

Cross-References

The following activities are classified elsewhere in the NAICS system:

Selling security alarm systems for buildings, without installation, repair, or monitoring services--are classified in Sector 42, Wholesale Trade, or Sector 44-45, Retail Trade;
Installing alarm systems (e.g., fire, burglar), without selling or monitoring services--are classified in Industry 238210, Electrical Contractors and Other Wiring Installation Contractors; and
Retailing motor vehicle security systems, with or without installation or repair services--are classified in Industry 441330, Automotive Parts and Accessories Retailers.

How to Use NAICS 561621 in SAM.gov

NAICS code 561621Security Systems Services (except Locksmiths) — is used in SAM.gov to identify businesses whose primary activity falls within this classification. When you add this code to your SAM.gov entity registration, contracting officers searching for vendors in the Investigation and Security Services space will be able to find your business.

If this code represents your primary business activity, designate it as your primary NAICS code. Your primary NAICS code determines your size standard for any contract solicited under this code. With a size standard of $25M average annual receipts, your business must be at or below this threshold to qualify as a small business for set-aside contracts under NAICS 561621.

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Frequently Asked Questions

What is NAICS code 561621?

NAICS code 561621 is 'Security Systems Services (except Locksmiths)', classified under the Administrative and Support and Waste Management and Remediation Services sector (NAICS 56). This U.S. industry comprises establishments primarily engaged in (1) selling security alarm systems, such as burglar and fire alarms, along with installation, repair, or monitoring services or (2) rem

What is the SBA small business size standard for NAICS code 561621?

The SBA defines a small business under NAICS code 561621 (Security Systems Services (except Locksmiths)) as one with $25M average annual receipts. This size standard determines eligibility for small business set-aside contracts, 8(a), HUBZone, WOSB, and SDVOSB programs in SAM.gov.

How do I register NAICS code 561621 in SAM.gov?

To register NAICS code 561621 in SAM.gov: (1) Log in at sam.gov, (2) Navigate to your Entity Registration, (3) Go to the Assertions section, (4) Add 561621 (Security Systems Services (except Locksmiths)) to your NAICS code list. You may designate one code as your Primary NAICS code.

Quick Actions

Related NAICS Codes

Other codes in Investigation and Security Services

Related PSC Codes

PSC codes commonly used with this NAICS sector

Source: GSA PSC Manual April 2025

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