How Check Security Features Work and the Types of Fraud They Prevent

High-security check stock carries multiple distinct security features, each designed to address a different fraud method. No single feature covers all three fraud vectors, which is why high-security stock is built in layers.

This post explains how each feature works, which fraud methods it addresses, and which it does not. It also covers how the feature set applies to pressure seal check formats, and how physical security features relate to Positive Pay as a complementary layer of protection.

What Types of Fraud Do Check Security Features Protect Against?

For a fuller treatment of the fraud environment and its operational implications, see When to Outsource Check Printing and Mailing.

Check washing uses chemical solvents to remove ink from the check. The fraudster intercepts a check, dissolves the payee name and dollar amount with bleach, acetone, or similar agents, and rewrites those fields. They leave the Magnetic Ink Character Recognition (MICR) line and signature intact. They then rewrite the check to a different payee or amount.

The Financial Crimes Enforcement Network (FinCEN) identified check washing as a primary driver of mail theft-related check fraud in its September 2024 Financial Trend Analysis.

Payee alteration is similar to check washing in principle, but here the check gets physically altered without chemicals. It is called payee alternation when a fraudster used correction fluid (Wite-Out), mechanical erasure, or overwriting directly on top of existing ink. The fraudster changes the payee name or amount through physical means rather than chemical removal.

Technically, check washing is a form of payee alteration because both result in the payee name or amount being changed on an existing check. However, the check security and banking industry treats them as distinct categories in practice because the defense mechanisms to prevent them are different.

Counterfeiting involves reproducing a check using the account and routing numbers visible on any intercepted check. It is very much a concern today because consumer-grade scanners can now capture check details at resolutions sufficient to reproduce security features that were adequate against lower-quality equipment a decade ago.

Security Feature Coverage by Fraud Type

The features below address these three fraud methods to varying degrees.

Security Feature	Check Washing	Counterfeiting	Payee Alteration
Void Pantograph	No	Yes	No
Chemical Sensitivity	Yes	No	No
Microprinting	No	Yes	No
Laid Lines	No	Partial	Yes
Artificial Watermark	No	Yes	No
Toner Adhesion	Partial	No	Yes
Fluorescent Fibers	No	Yes (authentication)	No
Security Screen	No	Yes	No
Thermochromic Ink	No	Yes (authentication)	No
Colored Background	No	Partial	No
Warning Band	No	No	Deterrent only

List of Check Security Features and How They Work

Void Pantograph

A void pantograph is a pattern printed into the background of a check that contains the word “VOID,” calibrated to the resolution thresholds of standard copiers and scanners. On the original check the pattern is nearly invisible. When the check is photocopied or scanned, “VOID” appears prominently across the face of the copy.

Standard reproduction equipment cannot translate the subtle contrast difference between the pantograph dots and the surrounding background with sufficient fidelity.

Chemical Sensitivity (Wash Detection)

Chemical sensitivity is a treatment applied to check paper that produces a visible reaction when exposed to bleach, acetone, hypochlorites, and other common washing agents. The reaction typically causes the paper to stain or discolor and activates a “VOID” indicator visible to the naked eye.

Some implementations include a dedicated wash detection box on the back of the check that makes tampering evident without close examination of the front.

Microprinting

Microprinting is text printed at a scale so small that it reads as a solid line to the naked eye. Under magnification it resolves into readable text. Common placements include the signature line, border lines, and around the MICR area.

In practice, standard copiers and scanners cannot reproduce text at that resolution: A photocopied or scanned check will show the microprint area as a dotted or broken line, visible under a loupe as evidence of reproduction.

Laid Lines

Laid lines are fine parallel lines printed across the face of the check in a specialized gray ink. If a section of the check is physically cut out and replaced, the lines will be visibly interrupted or misaligned. They are also difficult to replicate accurately with standard desktop inkjet printers.

Watermarks

High-security check stock uses one of two types of watermark. A true paper watermark is embedded during manufacturing: a dandy roll, a wire cylinder, presses a design into wet paper pulp before it dries, creating areas of varying thickness that appear lighter when held to light. Because it is structural rather than printed, it cannot be reproduced by a copier or scanner. True watermarks are most common on currency, government documents, and high-volume banking paper, though some business check stock uses them.

An artificial watermark is applied during printing in transparent or coin-reactive ink. It is not visible under normal examination but becomes visible when rubbed with a coin, held at an angle to the light, or examined under ultraviolet (UV) light. Artificial watermarks are more common on business check stock because they can be produced at commercial volumes and allow for customization. A counterfeit produced from a scan or photocopy will not reproduce the watermark correctly, making its absence a reliable indicator of a non-genuine document.

Toner Adhesion (Toner Lock)

Some high-security check paper includes a coating that causes laser toner to bond more strongly to the paper surface than standard stock. This makes it significantly more difficult to remove printed information using erasure or chemical treatment without visibly damaging the paper. It does not prevent washing agents from affecting the paper, but it makes clean removal of printed content harder.

Fluorescent Fibers

Fluorescent fibers are threads embedded in the paper during manufacturing that are visible only under ultraviolet light. Under normal lighting they are invisible. Under UV examination they glow in a characteristic pattern. As such, this is an authentication feature rather than a fraud deterrent. It allows a financial institution or examiner to confirm the check was printed on genuine high-security stock. A counterfeit printed on standard paper will not produce the UV response.

Security Screen

Many high-security checks include a printed security screen in the background. Words such as “ORIGINAL DOCUMENT” vanish or blur when photocopied, making the copy distinguishable from the original under direct comparison.

Warning Band and Padlock Icon

High-security checks carry a warning band, typically printed along the bottom back of the check, that lists the security features present and instructs the recipient to verify them before accepting the document.

The padlock icon is a registered certification mark of the Check Payment Systems Association (CPSA), used in accordance with the American National Standard ANSI X9.100-170. It signals that a check meets the minimum security feature requirements established by that standard and that the printer has been authorized by CPSA to use the mark.

Thermochromic Ink

Thermochromic ink changes color or disappears when exposed to heat and returns to its original color when it cools. On high-security check stock it typically appears as a colored element on the back of the check that vanishes when rubbed with a thumb or finger and reappears within seconds. It can be verified in the field without any equipment.

Colored Background

High-security checks are printed on a colored background tint applied across the face of the check. When a check is photocopied, the background color typically reproduces imperfectly or shifts in tone, making the copy distinguishable from the original.

What Security Features Does Standard Check Stock Leave Out?

Standard laser check stock is available through general commercial paper suppliers. It typically includes only a basic void pantograph and simple border design. Conversely, it does not include chemical sensitivity, artificial watermarks, fluorescent fibers, or toner adhesion treatments.

As a result, a check with no chemical sensitivity can be washed and rewritten. Similarly, a check with only a basic pantograph can potentially be reproduced on high-resolution printing equipment. So too, a check without microprinting has no reproduction-detection mechanism at the signature line. However, high-security stock addresses all three of these fraud types through layered security features, as explained above.

What Security Features Do Pressure Seal Checks Have?

Pressure seal checks are self-sealing. This means that the check and any accompanying stub or remittance information are printed on a single sheet of paper. This sheet then gets folds and sealed shut under pressure. Thus, it eliminates the need for a separate envelope.

The Seal as a Security Layer adds Tamper-resistance

Pressure seal checks must be torn open along the sides and top to access the contents. Thus, a check that arrives already opened has visibly damaged edges. Therefore, it is obvious that it has been tampered with before delivery.

High-volume disbursement programs, payroll runs, and benefit fund distributions commonly use pressure seal checks in part for this tamper-evidence, alongside the format’s postage and production advantages.

How Does Positive Pay Complement Physical Security Features?

Physical security features protect the check as a document. But Positive Pay protects the payment at the point of clearing: the bank matches every presented check against an authorized issue file before paying it. In this way, Positive Pay can catch counterfeits and altered checks that physical features did not prevent. Conversely, physical features stop fraud methods that Positive Pay does not see until after a check is already in circulation.

The Accredited Standards Committee X9 published a report in June 2026 finding that the combination of physical safeguards, detection tools, and procedural controls represents the most effective defense against check fraud — not any single measure in isolation.

For a full explanation of how Positive Pay works, its variants, and its legal implications, see: What Is Positive Pay and How Does It Help Prevent Check Fraud?

How Does Check Stock Choice Affect Fraud Protection?

Organizations should thoroughly examine the security features of their check stock.

For organizations printing in-house, not all MICR-compatible check stock carries the full security feature suite. Presently, high-security check stock is a specialty product generally available only through dedicated check printing suppliers and professional check printing and mailing vendors.

For organizations evaluating an outsource vendor, requesting the check stock specifications in writing is a reasonable part of the evaluation. The broader vendor evaluation criteria are covered in When to Outsource Check Printing and Mailing.

Secure Check Print and Mail Service by Tab Service Company

Tab Service Company prints checks on high-security MICR check stock, including pressure seal formats, and generates Positive Pay files for every production run. Our check printing and mailing operations run under SOC 2 Type II (Service Organization Control 2) compliance, independently audited by Plante Moran and pen-tested by HALOCK.

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