Written by Acorn Sales Company, manufacturing stamps and seals since 1964 · Reviewed by Holly R, VP of Sales and Marketing at Acorn Sales, against the Missouri Board of Geologist Registration and § 256.456.1 and.2, RSMo on 21 September 2026 · Updated 21 September 2026
A Missouri geologist seal is one and three-quarters inches in diameter, reads STATE OF MISSOURI above and REGISTERED GEOLOGIST below, and carries your name in printed letters with your certificate number preceded by the capital letters RG. 20 CSR 2145-2.100(1) states the whole design. Three points catch buyers out: the legend is REGISTERED GEOLOGIST, not Professional Geologist and not Licensed Professional Geologist; the number is a certificate number prefixed RG; and the name goes in printed letters, so a facsimile signature inside the circle is not what the rule asks for.
Missouri runs geologists through a different board and a different rule from its other design professions. Architects, engineers, land surveyors and landscape architects are licensed under Chapter 327, RSMo, and sealed under 20 CSR 2030-3.060. Geologists are registered under Chapter 256, RSMo, by the Missouri Board of Geologist Registration, and sealed under 20 CSR 2145-2.100. The two rules share a diameter and differ on everything that matters at the counter.
Placement is prescribed and it differs too. 20 CSR 2145-2.100(3) requires you to “affix his/her signature on or through his/her seal, and place the date of the signature under the seal on each sheet in a set of plans, drawings, specifications, maps, reports, and other documents” prepared by you or under your immediate personal supervision. Signature on or through the seal, date underneath it.
Missouri geologist seal requirements at a glance
| Requirement | Missouri rule | Source |
|---|---|---|
| Seal required | Yes | § 256.456.1 and.2, RSMo |
| Required elements | Concentric circles, STATE OF MISSOURI, REGISTERED GEOLOGIST, Your name in printed letters and Your certificate number preceded by RG | 20 CSR 2145-2.100(1) |
| Size and shape | One and three-quarters inches (1-3/4 inches) in diameter. 20 CSR 2145-2.100(1) requires each registered geologist to “secure a seal or rubber stamp, one and three-quarters inches (1 3/4″) in diameter.” One figure, no tolerance, and no separate dimension for the inner circle. | 20 CSR 2145-2.100(1) |
| Device allowed | 20 CSR 2145-2.100(2) provides that “The seal may be in the form of an embossing seal, a rubber stamp, or a computer-generated image, identical in size or design and content with the provisions of section (1) of. | 20 CSR 2145-2.100(2) |
| Signature and date | Placement is prescribed, and it differs from the other Missouri board. 20 CSR 2145-2.100(3) requires the registered geologist to “affix his/her signature on or through his/her seal, and place the date of the signature under the seal on each sheet in a set of plans, drawings, specifications, maps, reports, and other documents” prepared by the geologist or under the geologist’s immediate personal supervision. | 20 CSR 2145-2.100(3), (3)(A), (3)(B) |
| What must be sealed | Every sheet of plans, drawings, specifications, maps, reports and other documents prepared by the geologist or under immediate personal supervision, subject to the title or index page route in 20 CSR 2145-2.100(3)(A). | 20 CSR 2145-2.100(3), (4), (5) |
| Electronic seal | No named standard. 20 CSR 2145-2.100(2) permits a computer-generated image of the seal, identical in size or design and content with the prescribed design, but the rule sets no digital signature criteria, names no certificate authority and specifies no file format. | 20 CSR 2145-2.100(2) |
| Renewal and lapse | Missouri says this expressly for geologists, which the architects and engineers rule does not. 20 CSR 2145-2.100(6) provides that “Any registered geologist who does not have a current license in this state is prohibited from using his/her seal on any documents until the license is renewed or otherwise reinstated.” Renewal itself is governed by 20 CSR 2145-2.080. | 20 CSR 2145-2.100(6) |
| Firm requirements | No certificate of authority and no firm seal. | § 256.456.1, RSMo |
| Regulator | The Missouri Board of Geologist Registration | Sections 256.450 to 256.483, RSMo, chiefly §§ 256.453, 256.456, 256.462 and 256.471 |
Is a seal required in Missouri?
Missouri geologists answer to a different board and a different chapter from the state’s architects and engineers, and the duty is written into the practice statute rather than into a seal statute. Section 256.456.1, RSMo, provides that no person, firm or corporation shall engage in the practice of geology affecting public health, safety and welfare unless the work is performed by or under the supervision of a registered geologist, and that “All work so performed shall be signed and sealed by the registered geologist in responsible charge.” Section 256.456.2 adds that a geologic report required by or supporting compliance with municipal, county, state or federal law must be prepared by or under the supervision of a registered geologist “as evidenced by the registered geologist’s signature and seal.” The design is prescribed by 20 CSR 2145-2.100.
What must appear on the seal
- Concentric circles
- STATE OF MISSOURI
- REGISTERED GEOLOGIST
- Your name in printed letters
- Your certificate number preceded by RG
The rule states the design in full and leaves nothing open. 20 CSR 2145-2.100(1) requires that “The seal shall consist of concentric circles between which shall appear in capital letters ‘STATE OF MISSOURI’ on the upper part of the seal, and ‘REGISTERED GEOLOGIST’ on the lower part of the seal. Within the inner circle of the seal shall appear the name of the registered geologist in printed letters and his/her certificate number preceded by the capital letters ‘RG.’” Three points catch buyers out. The legend is REGISTERED GEOLOGIST, not Professional Geologist and not Licensed Professional Geologist. The number is prefixed RG and is a certificate number rather than a license number. And the name goes in printed letters, so a facsimile signature inside the circle is not what the rule asks for.
Size and shape
One and three-quarters inches (1-3/4 inches) in diameter. 20 CSR 2145-2.100(1) requires each registered geologist to “secure a seal or rubber stamp, one and three-quarters inches (1 3/4″) in diameter.” One figure, no tolerance, and no separate dimension for the inner circle. It matches the diameter the other Missouri design board uses, which is a coincidence of size rather than a shared rule.
Embosser, rubber stamp or digital
20 CSR 2145-2.100(2) provides that “The seal may be in the form of an embossing seal, a rubber stamp, or a computer-generated image, identical in size or design and content with the provisions of section (1) of this rule.” The rubber stamp is the safe buy, because subsection (3) requires the signature to go on or through the seal and an inked impression takes a pen, and because the computer-generated image has to match the physical design anyway.
Signing and dating
Placement is prescribed, and it differs from the other Missouri board. 20 CSR 2145-2.100(3) requires the registered geologist to “affix his/her signature on or through his/her seal, and place the date of the signature under the seal on each sheet in a set of plans, drawings, specifications, maps, reports, and other documents” prepared by the geologist or under the geologist’s immediate personal supervision. So the signature crosses the seal and the date sits beneath it. Subsection (3)(A) allows a single sealing point on multiple page work, letting the geologist “sign, seal, and date only the title or index page” where the signed sheet clearly identifies the other pages. Subsection (3)(B) requires a revising geologist to sign on the same line next to the revision date and explain the revision.
Different board, different rule, and the only Missouri seal rule that tells you when to stop using it
It is easy to assume Missouri runs geologists through the same seal rule as everyone else. It does not. Architects, engineers, land surveyors and landscape architects are licensed under Chapter 327, RSMo, and sealed under 20 CSR 2030-3.060. Geologists are registered under Chapter 256, RSMo, by the Missouri Board of Geologist Registration, and sealed under 20 CSR 2145-2.100.
The two rules look similar and differ in the details that matter at the counter. Both fix the diameter at 1-3/4 inches, but the geologist legend is REGISTERED GEOLOGIST where the Chapter 327 legends are Architect, Professional Engineer, Professional Land Surveyor and Professional Landscape Architect. The geologist prefix is RG, and it precedes a certificate number rather than a license number.
The placement rule also differs. 20 CSR 2030-3.060 says nothing about signing across the seal. 20 CSR 2145-2.100(3) is explicit: the signature goes “on or through” the seal and the date goes “under the seal”, on each sheet unless the title or index page route is used.
And 20 CSR 2145-2.100(6) answers the question the other rule leaves open. A registered geologist without a current license is prohibited from using the seal until the license is renewed or reinstated. That is a plain instruction, and it is the reason a geologist seal is worth keeping in a drawer rather than in a drafting kit during a lapse.
Which documents must be sealed
Every sheet of plans, drawings, specifications, maps, reports and other documents prepared by the geologist or under immediate personal supervision, subject to the title or index page route in 20 CSR 2145-2.100(3)(A). The statutory trigger in section 256.456, RSMo, is work affecting public health, safety and welfare and geologic reports required by or supporting compliance with law, with exemptions in section 256.471. Two prohibitions sit in the rule: subsection (5) says “Any documents not prepared by the registered geologist or under his/her personal supervision shall not be signed or sealed by the registered geologist”, and subsection (3)(C) tells a geologist whose seal appears in a multi-professional set to certify on the title or index page that the seal relates only to the portions involving the practice of geology as defined in section 256.453(7), RSMo.
Electronic and digital seals
No named standard. 20 CSR 2145-2.100(2) permits a computer-generated image of the seal, identical in size or design and content with the prescribed design, but the rule sets no digital signature criteria, names no certificate authority and specifies no file format. Checked 20 CSR 2145-1, 2145-2 and 2145-3 and Chapter 256, RSMo. The safe electronic practice is an image that matches the physical die, carrying the signature on or through it and the date beneath it, exactly as subsection (3) describes for paper.
Renewal, lapse and retirement
Missouri says this expressly for geologists, which the architects and engineers rule does not. 20 CSR 2145-2.100(6) provides that “Any registered geologist who does not have a current license in this state is prohibited from using his/her seal on any documents until the license is renewed or otherwise reinstated.” Renewal itself is governed by 20 CSR 2145-2.080. The rule does not require the seal to be destroyed or surrendered, and neither the rule nor Chapter 256, RSMo, says whether a certificate number survives reinstatement, so confirm the RG number before reordering after a gap.
Firm requirements
No certificate of authority and no firm seal. Section 256.456.1, RSMo, regulates the work rather than the entity: no person, firm or corporation may engage in the practice of geology affecting public health, safety and welfare unless the work is performed by or under the supervision of a registered geologist, and that geologist signs and seals it. Nothing in Chapter 256, RSMo, or 20 CSR 2145 requires a firm registration number on a report or creates a corporate geology seal. Note that the certificate of authority scheme in 20 CSR 2030-10.010 belongs to the architects and engineers board and does not reach geology.
What to check before you order
Order a 1-3/4 inch die with concentric circles and capital letters. STATE OF MISSOURI on the upper part of the ring, REGISTERED GEOLOGIST on the lower part, and inside the inner circle your name in printed letters with your certificate number preceded by RG. Take the rubber stamp as your working device, because you sign on or through the seal and date it underneath. An embosser or a computer-generated image is also lawful so long as it is identical in size or design and content to the prescribed design. No proof of registration is required at the counter and nothing is filed with the board.
Browse geologist stamps and seals.
Frequently asked questions
Is a geologist seal required in Missouri?
Yes, and the duty sits in the practice statute. Section 256.456.1, RSMo, provides that no person, firm or corporation shall engage in the practice of geology affecting public health, safety and welfare unless the work is performed by or under the supervision of a registered geologist, and that “All work so performed shall be signed and sealed by the registered geologist in responsible charge.” Section 256.456.2 adds geologic reports required by or supporting compliance with municipal, county, state or federal law.
What size is a Missouri geologist seal?
One and three-quarters inches in diameter, under 20 CSR 2145-2.100(1), which requires each registered geologist to secure a seal or rubber stamp at that figure. One dimension, no tolerance and no separate figure for the inner circle. It happens to match the diameter the other Missouri design board uses, which is a coincidence of size rather than a shared rule.
What exactly goes on the face?
Concentric circles with STATE OF MISSOURI in capitals on the upper part and REGISTERED GEOLOGIST in capitals on the lower part, and inside the inner circle your name in printed letters with your certificate number preceded by RG. That is the complete design in 20 CSR 2145-2.100(1), and nothing else belongs on it.
Embosser, rubber stamp or computer image?
All three. 20 CSR 2145-2.100(2) permits “an embossing seal, a rubber stamp, or a computer-generated image, identical in size or design and content with the provisions of section (1) of this rule.” The rubber stamp is the practical working device, because subsection (3) requires your signature on or through the seal and an inked impression takes a pen.
Where do the signature and date go?
Signature on or through the seal, date under the seal, on each sheet. That is 20 CSR 2145-2.100(3). Subsection (3)(A) allows a single sealing point on multiple page work, letting you “sign, seal, and date only the title or index page” where the signed sheet clearly identifies the other pages.
How do revisions get handled?
20 CSR 2145-2.100(3)(B) requires a revising geologist to sign on the same line next to the revision date and explain the revision. That keeps the revision history legible on the face of the document rather than in a separate log.
What if my seal appears in a set with other professions?
Certify the scope. 20 CSR 2145-2.100(3)(C) tells a geologist whose seal appears in a multi-professional set to certify on the title or index page that the seal relates only to the portions involving the practice of geology as defined in section 256.453(7), RSMo.
Can I seal work someone else prepared?
No. 20 CSR 2145-2.100(5) is flat: “Any documents not prepared by the registered geologist or under his/her personal supervision shall not be signed or sealed by the registered geologist.” The statutory trigger for sealing at all is work affecting public health, safety and welfare and geologic reports required by or supporting compliance with law, with exemptions in section 256.471.
Can I seal while my Missouri registration is lapsed?
No, and Missouri says so expressly for geologists where its other design rule does not. 20 CSR 2145-2.100(6) provides that “Any registered geologist who does not have a current license in this state is prohibited from using his/her seal on any documents until the license is renewed or otherwise reinstated.” Renewal is governed by 20 CSR 2145-2.080. Neither the rule nor Chapter 256 says whether the certificate number survives reinstatement, so confirm your RG number before reordering after a gap.
How do I seal a PDF in Missouri?
With an image that matches the physical die. 20 CSR 2145-2.100(2) permits a computer-generated image identical in size or design and content with the prescribed design, and the rule sets no digital signature criteria, names no certificate authority and specifies no file format. The safe practice is to carry the signature on or through the image and the date beneath it, exactly as subsection (3) describes for paper.
Does a Missouri geology firm need a certificate of authority?
No. Section 256.456.1, RSMo, regulates the work rather than the entity, and nothing in Chapter 256 or 20 CSR 2145 requires a firm registration number on a report or creates a corporate geology seal. The certificate of authority scheme in 20 CSR 2030-10.010 belongs to the architects and engineers board and does not reach geology.
