Identify Prohibited Activities — Identify other prohibited...

SECTION 1

Historical Context & Motivation

The securities industry in the United States has long grappled with the tension between enabling capital formation and protecting investors from fraud, manipulation, and misuse of their assets. Before modern regulation, the markets were rife with practices that would today be classified as prohibited activities — from brokerage firms commingling customer funds with proprietary capital to unregistered individuals soliciting orders from the public. These abuses eroded investor confidence and contributed to devastating market crashes, prompting Congress and self-regulatory organizations to construct layers of statutory and rule-based protections that define the compliance landscape every associated person must navigate today.

1929–1933

Market Crash & Senate Investigations

The Pecora Commission hearings exposed rampant fraud, commingling of customer assets, and sale of unregistered securities by bank affiliates, galvanizing public support for federal securities regulation.

1933–1934

Securities Act & Exchange Act

Congress enacted the Securities Act of 1933 (requiring registration of securities) and the Securities Exchange Act of 1934 (creating the SEC and requiring broker-dealer registration), establishing the foundational prohibition against unregistered activity.

1970

SIPC Created

The Securities Investor Protection Act of 1970 established SIPC to protect customers when broker-dealers fail, directly addressing the problem of firms improperly using customer funds.

2002

Sarbanes-Oxley Act

Following the Enron and WorldCom scandals, SOX enhanced protections for investor assets and imposed stricter penalties for improper handling of funds and deceptive practices.

2010

Dodd-Frank Act

Post-financial-crisis reform strengthened enforcement powers, expanded registration requirements, and increased penalties for prohibited activities including misuse of customer assets and operating without proper registration.

This regulatory evolution raises a central question for every securities professional: what specific activities are prohibited under current law and self-regulatory organization (SRO) rules, and how do violations related to improper use of funds and unregistered activity differ from one another? Understanding the full taxonomy of prohibited conduct is essential not only for passing the SIE exam but for maintaining the ethical standards that undergird investor trust.

SECTION 2

Core Principles & Definitions

The regulatory framework governing prohibited activities rests on several foundational principles. These principles derive from the overarching mandate of securities law: to protect investors, maintain fair and efficient markets, and facilitate capital formation. When a registered representative, broker-dealer, or investment adviser engages in any of the activities outlined below, they violate one or more of these core principles and face disciplinary action from FINRA, the SEC, or both.

Improper Use of Customer Funds

Using, borrowing, or commingling customer money or securities for purposes not authorized by the customer. This includes unauthorized trading in discretionary accounts, misappropriation, and failure to segregate customer funds from firm proprietary capital.

Unregistered Activity

Conducting securities business — including soliciting orders, providing investment advice for compensation, or effecting transactions — without proper registration as a broker-dealer, investment adviser, or associated person, or while under a statutory disqualification.

Selling Away (Private Securities Transactions)

Participating in securities transactions outside the scope of one's employing firm without providing prior written notice to the firm. This deprives the firm of its supervisory obligation and exposes customers to unvetted risks.

Borrowing From or Lending to Customers

Unless the firm has written policies permitting it and specific conditions are met (such as the customer being a family member or a financial institution), registered representatives are prohibited from entering into lending arrangements with customers.

Guarantees & Sharing in Customer Accounts

Guaranteeing a customer against loss or guaranteeing specific returns is strictly prohibited. Sharing in customer gains and losses is only allowed under narrow conditions with prior firm approval and proportional contribution of capital.

✦ KEY TAKEAWAY

Think of the securities regulatory framework like the trust architecture of a bank vault. The customer's assets are stored inside the vault (segregated accounts), and only authorized, registered personnel with the right keys (registration and licensing) may access them for authorized purposes. An unregistered person attempting to handle securities transactions is like someone without clearance trying to open the vault — even if their intentions are benign, the system treats the breach as a critical security failure because the protective controls were circumvented.

SECTION 3

Visual Explanation — Taxonomy of Prohibited Activities

This diagram illustrates the three major branches of prohibited activities tested on the SIE exam. The left branch covers improper use of funds (commingling, misappropriation, unauthorized trading), the center branch addresses unregistered activity (unregistered persons and unregistered securities), and the right branch captures other violations including selling away, guarantees, and improper borrowing/lending.

The diagram above provides a structured overview that should serve as a mental map when studying prohibited activities. Notice that each branch represents a distinct regulatory concern. Improper use of funds threatens the safety of customer assets, unregistered activity undermines the qualification and oversight mechanisms that regulators depend on, and the other violations category captures conduct that creates conflicts of interest or exposes customers to unmonitored risks. On the SIE exam, questions frequently present realistic scenarios and ask candidates to identify which specific prohibition has been violated, so internalizing this taxonomy is critical.

SECTION 4

How Prohibited Activities Operate in Practice

Improper Use of Customer Funds — Detailed Mechanism

Under SEC Rule 15c3-3 (the Customer Protection Rule), broker-dealers must maintain physical possession or control of all fully paid and excess margin securities carried for customer accounts. The rule also mandates a weekly computation to determine how much cash the firm owes customers versus how much it holds, and any shortfall must be deposited into a Special Reserve Bank Account exclusively for customer benefit. Improper use of funds violations occur when firms fail to perform this segregation, divert customer cash to fund proprietary trading, or when individual representatives convert customer assets for personal use.

Commingling refers to mixing customer funds with firm proprietary funds in the same accounts. This is prohibited because it makes it impossible to trace which dollars belong to which party, and it exposes customer capital to the firm's own business risks — including potential insolvency. Misappropriation (also called conversion) is the most severe form: a representative or firm takes customer money or securities and uses them for an unauthorized purpose, such as paying personal expenses or covering the firm's operating losses. This constitutes both a regulatory violation and potentially a criminal offense — theft.

Unregistered Activity — Detailed Mechanism

Section 15(a) of the Securities Exchange Act of 1934 prohibits any person from acting as a broker or dealer in securities unless registered with the SEC. Similarly, FINRA rules require that any person associated with a member firm who engages in the securities business must pass qualifying examinations and register through the Central Registration Depository (CRD). Unregistered activity takes two forms: an unregistered person conducting securities business, or the offer and sale of unregistered securities that do not qualify for an exemption (such as Regulation D, Regulation A, or Rule 144). Both forms defeat the disclosure and oversight mechanisms that Congress designed to protect investors.

⚠️ Statutory Disqualification

A person may be subject to statutory disqualification if they have been expelled or suspended from an SRO, convicted of certain felonies or securities-related misdemeanors within the past 10 years, or are subject to an SEC or court order barring them from the industry. A statutorily disqualified person who engages in securities activity is committing unregistered activity even if they previously held a valid registration.

Other Prohibited Activities — Selling Away, Guarantees, and Lending

Selling away occurs under FINRA Rule 3280 (Private Securities Transactions) when an associated person participates in a securities transaction outside the regular scope of their employment without providing prior written notice to their member firm. Even if the transaction itself is legitimate, the failure to notify the firm removes supervisory oversight and creates liability exposure. If the transaction involves compensation, the firm must approve it and treat it as if it occurred under the firm's own operations.

Guaranteeing against loss is prohibited because it fundamentally distorts the risk-return relationship. FINRA Rule 2150 states that no member or associated person may guarantee a customer against loss in connection with any securities transaction or in any securities account. Similarly, sharing in customer accounts is only permissible when the associated person has received prior written authorization from both the customer and the firm, and shares in gains and losses proportional to their own financial contribution — with a narrow exception for immediate family members, who may share disproportionately.

Borrowing from or lending to customers is governed by FINRA Rule 3240. The rule establishes five permissible categories of lending arrangements, which include: the customer is a financial institution that regularly engages in lending; the customer and representative are both registered with the same firm; the customer is an immediate family member; the arrangement is based on a pre-existing personal relationship; or the arrangement is based on a business relationship outside the broker-customer relationship. In all cases except the family member exception, the firm must have written procedures in must approve the arrangement.

SECTION 5

Detailed Classification — Violation Types, Rules & Consequences

The enforcement pathway diagram shows how violations move from detection through investigation to sanctions across three regulatory tiers — FINRA disciplinary actions, SEC civil enforcement, and DOJ criminal prosecution. The severity spectrum at the bottom ranks violations from procedural failures to outright theft.

Comprehensive classification of prohibited activities with governing rules and enforcement consequences

Prohibited Activity	Primary Rule / Statute	Key Elements	Typical Sanctions
Commingling	SEC Rule 15c3-3	Mixing customer and firm funds; failure to maintain Special Reserve Account	Fine, suspension, firm sanctions, potential criminal referral
Misappropriation / Conversion	Exchange Act §10(b); FINRA Rule 2010	Taking customer assets for unauthorized use; theft of securities or cash	Industry bar, disgorgement, criminal prosecution
Unregistered Broker-Dealer	Exchange Act §15(a)	Effecting transactions without SEC/FINRA registration; acting while statutorily disqualified	Cease-and-desist, disgorgement, civil penalties, criminal charges
Unregistered Securities	Securities Act §5	Offering/selling securities without registration statement or valid exemption	Rescission rights for investors, SEC action, criminal referral
Selling Away	FINRA Rule 3280	Private securities transactions without prior written notice to employing firm	Fine, suspension, or bar from industry
Guarantees Against Loss	FINRA Rule 2150	Promising a customer will not lose money; guaranteeing a specific rate of return	Fine, suspension, potential bar
Borrowing/Lending	FINRA Rule 3240	Lending to or borrowing from customers outside permitted categories or without firm approval	Fine, suspension, potential bar

SECTION 6

Worked Example — Identifying the Violation

The following scenario illustrates how to apply the taxonomy of prohibited activities to a realistic fact pattern, the kind you will encounter on the SIE examination.

📋 SCENARIO

Marcus is a registered representative at XYZ Securities. His long-time client, Mrs. Chen, asks Marcus to invest $200,000 in a private real estate limited partnership that Marcus's college friend is managing. Marcus does not notify XYZ Securities about the transaction. He executes the paperwork directly, receives a $15,000 referral fee from his friend, and deposits it into his personal bank account. Mrs. Chen later discovers that the partnership was never registered with the SEC and does not qualify for a Regulation D exemption. What prohibited activities has Marcus committed?

Analyzing Marcus's Conduct

Step 1 — Identify Selling AwayMarcus participated in a securities transaction (the sale of limited partnership interests) outside the regular course of his employment with XYZ Securities. Under FINRA Rule 3280, he was required to provide prior written notice to his firm before participating in this private securities transaction. He failed to do so, and he received compensation ($15,000 referral fee), which means the firm would have needed to not only be notified but also approve the transaction and supervise it.

Violation: Selling away (FINRA Rule 3280)

Step 2 — Identify Unregistered Securities ViolationThe limited partnership interests are securities under the Securities Act of 1933. Mrs. Chen's investment was in a partnership that was neither registered with the SEC nor covered by a valid exemption such as Regulation D. Under Section 5 of the Securities Act, it is illegal to offer or sell securities unless a registration statement is in effect or an exemption applies. Marcus facilitated the sale of unregistered securities.

Violation: Sale of unregistered securities (Securities Act §5)

Step 3 — Assess Undisclosed CompensationMarcus received a $15,000 referral fee that he deposited into his personal account without disclosing it to his firm or his client. This represents undisclosed compensation outside the scope of his employment — a direct violation of FINRA rules governing outside business activities and compensation. Additionally, the failure to disclose this payment to Mrs. Chen constitutes a material omission that could form the basis of a fraud claim.

Violation: Undisclosed compensation; potential fraud (FINRA Rule 2010, Exchange Act §10(b))

Step 4 — Consider Supervisory FailuresWhile Marcus is the primary violator, XYZ Securities could also face regulatory scrutiny. If the firm's supervisory procedures were inadequate to detect or prevent selling away — for instance, if it did not require associated persons to certify outside business activities or did not monitor for unusual account activity — the firm could be cited for failure to supervise under FINRA Rules 3110 and 3120.

Potential firm-level violation: Failure to supervise (FINRA Rules 3110/3120)

Step 5 — Determine Likely ConsequencesGiven the multiple overlapping violations — selling away, unregistered securities, undisclosed compensation — Marcus faces severe sanctions. FINRA would likely impose an industry bar, a substantial fine, and order disgorgement of the $15,000 fee. The SEC could bring a civil enforcement action, and the Department of Justice could pursue criminal charges for securities fraud. Mrs. Chen would have rescission rights, allowing her to recover her $200,000 investment.

Likely outcome: Industry bar, fines, disgorgement, possible criminal prosecution

SECTION 7

Comparing Prohibited Activities — Common Exam Distinctions

SIE exam questions often test whether candidates can distinguish between similar-sounding violations. The table below highlights the most commonly confused pairs and the key factors that differentiate them.

Common distinctions tested on the SIE examination

Activity A	Activity B	Key Distinction
Commingling	Misappropriation	Commingling is the failure to separate customer and firm assets. Misappropriation is the unauthorized taking or use of customer assets. Commingling is the precondition; misappropriation is the active theft.
Selling Away	Outside Business Activity	Selling away involves a securities transaction outside the firm. An outside business activity (FINRA Rule 3270) involves non-securities employment or business. Both require written notice, but selling away specifically involves securities.
Unregistered Person	Unregistered Securities	An unregistered person lacks broker-dealer or representative registration. Unregistered securities lack an effective registration statement and no exemption. A registered person can still violate the law by selling unregistered securities.
Guarantee Against Loss	Sharing in Account	A guarantee promises the customer will not lose money — always prohibited. Sharing in an account means sharing gains and losses — permitted under strict conditions (written authorization, firm approval, proportional contributions).
Unauthorized Trading	Churning	Unauthorized trading is executing trades without customer consent. Churning involves excessive trading to generate commissions — the customer may have given discretion, but the rep abuses it. Both are prohibited, but the mechanisms differ.

✦ KEY TAKEAWAY

When analyzing exam scenarios, apply a systematic checklist: (1) Is the person properly registered? (2) Is the security properly registered or exempt? (3) Were customer funds handled according to segregation rules? (4) Was the firm notified and did it approve the activity? (5) Were there any guarantees, unauthorized trades, or improper lending arrangements? Walking through these five checkpoints will help you identify the specific violation even in complex, multi-layered fact patterns.

SECTION 8

Connection to Advanced Regulatory Topics

The prohibited activities covered in this lesson form the foundation for more complex regulatory topics that candidates will encounter on subsequent licensing examinations (Series 7, Series 66, Series 63) and in professional practice. Understanding how these foundational prohibitions connect to advanced compliance concepts will deepen your analytical capabilities and provide context for why the SIE tests them so heavily.

SIE concepts and their advanced regulatory extensions

SIE-Level Concept	Advanced Extension	Where You'll See It
Improper use of customer funds	Net capital rule compliance (Rule 15c3-1), customer reserve computations, hypothecation restrictions	Series 7; Series 24 (Principal)
Unregistered person	State-level registration (blue sky laws), investment adviser registration under the Advisers Act, dual registration requirements	Series 63; Series 65/66
Unregistered securities	Detailed analysis of exemptions (Reg D, Reg A+, Rule 144, 144A), crowdfunding under Reg CF, state notice filing	Series 7; Series 79 (IB)
Selling away	Firm supervisory systems design (FINRA Rule 3110), branch office inspections, electronic surveillance, annual compliance certifications	Series 24; Series 9/10
Guarantees and account sharing	Fiduciary standards, performance-based fee rules under the Advisers Act, hedge fund side letters, managed account structures	Series 65/66; Series 7

As you progress through your securities career, you will find that the prohibited activities you study at the SIE level are not merely exam topics — they define the operational boundaries within which every compliant firm must function. The most significant enforcement actions in recent history, from the Madoff Ponzi scheme (which involved both misappropriation and unregistered activity) to numerous cases of selling away at major wirehouses, all trace back to these fundamental prohibitions. Building fluency in these concepts now will serve you throughout your career.

SECTION 9

Practice Problems

PROBLEM 1 — CONCEPTUAL

A broker-dealer firm deposits customer cash into the same bank account it uses for its own operating expenses. Which specific prohibited activity does this represent, and what is the primary regulatory concern?

PROBLEM 2 — BASIC CALCULATION

A registered representative receives a $10,000 referral fee from a private securities transaction that she did not report to her member firm. Under FINRA Rule 3280, what was she required to do before participating in this transaction, and what would the firm's responsibilities have been once notified?

PROBLEM 3 — INTERMEDIATE

David, a registered representative, tells his client: 'I personally guarantee that if you invest $50,000 in this mutual fund, you will earn at least 8% annually, and if the fund loses money, I will cover the loss out of my own pocket.' David also proposes that they share equally in the account's gains and losses, even though David is contributing only 20% of the capital. Identify all prohibited activities in this scenario.

PROBLEM 4 — APPLIED

An individual who was barred from the securities industry three years ago for fraud establishes a consulting firm that provides 'financial education seminars.' During these seminars, she recommends specific stocks, accepts compensation from attendees for personalized portfolio reviews, and facilitates purchases of those stocks through an online brokerage by placing orders on behalf of attendees. Analyze whether this constitutes unregistered activity and identify all applicable regulatory provisions.

PROBLEM 5 — CRITICAL THINKING

Consider a scenario where a registered representative at a FINRA member firm borrows $25,000 from a long-standing client who is also a personal friend. The firm has written policies permitting borrowing based on personal relationships outside the broker-customer relationship, and the representative receives firm approval. However, the representative uses the borrowed funds to cover personal margin calls in his own brokerage account at a different firm. Six months later, the client requests repayment, but the representative cannot repay because the margin positions resulted in losses. Evaluate whether any prohibited activities occurred, considering both the lending arrangement itself and the representative's subsequent conduct.

SUMMARY

Summary — Prohibited Activities: Improper Use of Funds & Unregistered Activity

Prohibited activities in the securities industry fall into three major categories. Improper use of customer funds encompasses commingling (mixing customer and firm funds), misappropriation (converting customer assets), and unauthorized trading (executing trades without customer consent), all governed primarily by SEC Rule 15c3-3 and FINRA conduct rules. Unregistered activity includes both unregistered persons conducting securities business in violation of Exchange Act §15(a) and unregistered securities offered without registration or exemption under Securities Act §5.

Other critical prohibitions include selling away (private securities transactions without firm notification under FINRA Rule 3280), guaranteeing against loss (always prohibited under FINRA Rule 2150), disproportionate sharing in customer accounts, and improper borrowing from or lending to customers outside the five permitted categories under FINRA Rule 3240. Violations trigger enforcement at multiple levels — FINRA disciplinary actions, SEC civil proceedings, and DOJ criminal prosecution — with consequences ranging from fines and suspension to industry bars and imprisonment.