Signature Certification: Issuers, Dollar Limits, and What to Bring

A medallion signature guarantee is a specialized stamp applied by a participating bank, credit union, or broker-dealer that certifies your signature on documents transferring securities, and it makes that institution financially liable if the signature turns out to be forged or unauthorized. Transfer agents require it before they will move stocks, bonds, or mutual fund shares between owners or accounts, and a regular notary cannot substitute for it. To get one, you visit an institution where you already have an account, bring the right documents, and sign in front of an authorized officer who then applies the stamp.

When You Need One

The most common trigger is holding securities in physical certificate form and wanting to transfer or sell them. A transfer agent will not accept your instructions on signed certificates or stock power forms without a medallion guarantee.¹

Other situations that typically require one:

Changing the registered name on an account.
Transferring shares to a different owner after a death or divorce.
Moving holdings between brokerage firms.
Adding or removing a beneficiary.
Large redemptions or withdrawals from a mutual fund or brokerage, above a threshold that varies by institution.

If you aren’t sure whether your transaction needs one, call the transfer agent or your brokerage before scheduling an appointment. The answer determines everything else.

What the Stamp Actually Guarantees

A medallion guarantee is not identity verification. Under the Uniform Commercial Code, the stamping institution warrants three things at once: that your signature is genuine, that you are the right person to sign (or that your agent has actual authority), and that you have the legal capacity to sign.

Those warranties are backed by a surety bond. If a transfer agent processes a fraudulent transaction based on a stamped document, the guaranteeing institution owes the transfer agent for the loss, up to the bond limit printed on the stamp. That exposure is why banks treat the process carefully and why they generally won’t stamp documents for someone they don’t already know as a customer.

SEC Rule 17Ad-15 requires registered transfer agents to accept guarantees from any eligible guarantor institution and to publish their written acceptance standards on request.²

Who Can Issue One

Not every financial institution qualifies. Federal rules limit eligible guarantors to banks, broker-dealers, credit unions, savings associations, national securities exchanges, and clearing agencies.² Beyond that, the institution must belong to one of three recognized medallion programs:

Securities Transfer Agents Medallion Program (STAMP), the largest, covering more than 7,000 U.S. and Canadian institutions.
Stock Exchanges Medallion Program (SEMP), whose participants include regional stock exchange member firms, clearing companies, and trust companies.
New York Stock Exchange Medallion Signature Program (MSP), whose participants include NYSE member firms.

An institution outside these programs cannot issue a medallion guarantee, no matter how large or well-known.¹ Confirm program membership before you make the trip. Participation has thinned in recent years, so finding a provider can take some calling around.

Most participating institutions provide the service only to existing customers. Some require that your account has been open for a minimum period, with six months being a common tenure requirement at larger banks. Established customers often get the service free; some institutions charge a fee in the range of $10 to $50.

Check the Stamp’s Dollar Limit First

Every medallion stamp has an alpha prefix that tells the transfer agent how much surety coverage backs it. If your transaction exceeds the stamp’s limit, the transfer agent will reject it. STAMP prefixes run as follows:

Prefix E or F: up to $100,000 (F is designated for credit unions).
Prefix D: up to $250,000.
Prefix C: up to $500,000.
Prefix B: up to $750,000.
Prefix A: up to $1,000,000.
Prefix X: up to $2,000,000.
Prefix Y: up to $5,000,000.
Prefix Z: up to $14,000,000.

A small community bank or credit union often carries only an E or D prefix. If you are transferring a portfolio worth more than that, you need to find an institution with a higher-tier stamp. Large broker-dealers and major banks are more likely to carry X, Y, or Z. Call ahead and ask what prefix the branch carries before you go.

What to Bring

Show up without the right paperwork and the branch will send you home. Gather everything in advance:

A current government-issued photo ID (driver’s license or U.S. passport). The name on the ID must match the account registration exactly.
Proof of ownership: a recent brokerage or account statement showing the securities in your name, or the physical certificate itself.
A stock power form, obtained from the transfer agent or the institution managing the account. Fill in the issuing company’s name, your account number, and the number of shares, but leave the signature line blank until you are in front of the guaranteeing officer.
Any additional transfer documents the transfer agent requires. Confirm the list with them in advance.

Signing on Behalf of Someone Else

If you are signing as someone other than the account holder, bring more paperwork. Executors and personal representatives need a death certificate plus court-issued letters testamentary or letters of administration; a will alone is not enough. Trustees typically need a trust certification or the relevant pages of the trust agreement showing their authority. Exact requirements vary by institution, so call first.

Power of attorney is a harder case. Some institutions refuse to issue a medallion guarantee for an agent acting under a power of attorney, because the liability risk is higher when the actual account holder is not present. Confirm acceptance in advance. If the institution won’t do it, contact the transfer agent to ask about alternatives.

A Notary Public Is Not a Substitute

This is the most common misunderstanding, and acting on it will cost you time. A notary and a medallion signature guarantor do different jobs, and a transfer agent will reject notarized paperwork when a medallion was required.

A notary confirms that the signer appeared in person and showed identification. The notary takes on no financial responsibility if the signature is fraudulent. A medallion guarantee makes the stamping institution financially liable, backed by a surety bond, for losses from a forged or unauthorized signature. That bond is what gives transfer agents the confidence to process high-value ownership changes. Only authorized personnel at participating institutions can apply the stamp. A notary cannot perform medallion services unless that same person is also an authorized employee of a participating institution acting in that separate capacity.

The Signing Visit

The process is face-to-face. You cannot complete it by mail, phone, or video. At the branch, a designated officer reviews your ID, verifies your ownership of the securities, and examines the transfer documents for completeness. The officer watches you sign the stock power and any certificates, then applies the stamp directly to the signed documents.

The stamp carries the institution’s unique identification number, the alpha prefix showing surety coverage, and security features meant to prevent tampering. Once stamped, the documents are ready to go to the transfer agent.

Submitting the Stamped Documents

Send the originals to the transfer agent’s processing center by overnight or tracked delivery. Physical securities certificates are difficult to replace, and losing them in transit means surety bonds and additional paperwork. Make photocopies before mailing.

There is no universal federal expiration date on a medallion stamp, but individual transfer agents set their own acceptance windows and some will reject a stamp they consider stale. Submit promptly. If weeks pass between getting the stamp and sending the paperwork, call the transfer agent to confirm it will still be accepted.

If You Don’t Have an Account at a Participating Institution

Without an existing relationship, getting a guarantee is significantly harder. Most banks and brokerages will not guarantee a non-customer’s signature because of the liability.¹ Start with any bank, credit union, or broker-dealer where you already do business. If none participate, consider opening an account at one that does, keeping in mind the tenure requirement some institutions impose before you qualify for the service.

Investors living overseas may be able to use an overseas branch of a U.S. or Canadian bank, broker, or credit union where they already hold an account.¹ If that isn’t available, contact the transfer agent or the issuing company. Some transfer agents maintain alternative verification procedures, such as phone security protocols or enhanced identity questions, for shareholders who genuinely cannot access a medallion program.

Common Reasons a Guarantee Gets Rejected

A rejection sends you back to square one and delays the transfer by days or weeks. The frequent causes are preventable:

The transaction value exceeds the stamp’s surety limit. If you are moving $300,000 in securities and your bank carries only a D-prefix stamp capped at $250,000, the transfer agent will reject it.
Documents are incomplete or names don’t match across your ID, the account registration, and the stock power. If your name has changed by marriage or court order, bring supporting records.
The guaranteeing institution isn’t a current program member. Transfer agents check stamps against the program’s database, and a lapsed membership makes the guarantee worthless.
The transaction looks irregular. A guarantor should decline when something is off, such as a sudden address change followed immediately by a transfer request, or instructions that don’t match the account’s history.

If your guarantee is rejected, the transfer agent must notify both you and the guarantor of the rejection and its specific reasons within two business days.² That notice tells you what to fix before trying again.

1
Investor.gov. Medallion Signature Guarantees: Preventing the Unauthorized Transfer of Securities
2
eCFR. 17 CFR 240.17Ad-15 – Signature Guarantees