It is required when YOU decide it is. The law is intended to protect you and not to appease some public agency.
I use my seal as a QA/QC verification.
CALIFORNIA CODE OF REGULATIONS:
411. Seal and Signature.
(a) The seal required by Section 6764 of the Code shall be not less than one and one-half
(1½) inches in diameter and shall contain the following information:
(1) Within the top border of seal: Either “Professional Engineer,” “Registered
Professional Engineer,” or “Licensed Professional Engineer.”
(2) Within the bottom border of seal: “State of California.”
(3) In the center of seal:
(A) Licensee’s name as it appears on the certificate issued by the Board or as
abbreviated pursuant to subdivision (d);
(B) Number of certificate or authority; and,
(C) Branch or authority of engineering in which licensed.
The seal shall be of a design similar to those shown below and shall bear at minimum
those elements specified above.
(b) The seal authorized by Section 8750 of the Code shall be not less than one and onehalf (1 ½) inches in diameter and shall contain the following information:
(1) Within the top border of the seal: Either “Professional Land Surveyor” or
“Licensed Land Surveyor.”
(2) Within the bottom border of the seal: “State of California.”
(3) In the center of the seal:
(A) Licensee’s name as it appears on the certificate issued by the Board or as
abbreviated pursuant to subdivision (d); and,
(B) Number of certificate.
The seal shall be of a design similar to those shown below and shall bear at minimum
those elements specified above.
(c) The seal may be obtained by the licensee from any source.
(d) The seal may contain an abbreviated form of the licensee’s given name or a
combination of initials representing the licensee’s given name provided the surname listed with
the Board appears on the seal and in the signature.
(e) The seal shall be capable of leaving a permanent ink representation, a permanent
impression, or an electronically-generated representation on the documents. The signature may
be applied to the documents electronically.
(f) Preprinting of blank forms with the seal or signature, the use of decals of the seal or
signature, or the use of a rubber stamp of the signature is prohibited.
(g) (1) All professional engineering plans, specifications, reports, or documents
(hereinafter referred to as “documents”) shall be signed and sealed in accordance with the
requirements of the Professional Engineers Act and any other laws related to the practice of
professional engineering and shall be signed and sealed in a manner such that all work can be
clearly attributed to the licensee(s) in responsible charge of the work.
(2) All maps, plats, reports, descriptions, or other professional land surveying
documents (hereinafter referred to as “documents”) shall be signed and sealed in accordance
with the requirements of the Professional Land Surveyors’ Act and any other laws related to the
practice of professional land surveying and shall be signed and sealed in a manner such that all
work can be clearly attributed to the licensee(s) in responsible charge of the work.
(3) When signing and sealing documents containing work done by, or under the
responsible charge of, two or more licensees, the signature and seal of each licensee in
responsible charge shall be placed on the documents with a notation describing the work done
under each licensee’s responsible charge.
(h) Each licensee shall include the date of signing and sealing immediately below or next
to the signature and seal.
https://www.bpelsg.ca.gov/laws/boardrul ... otated.pdf