Regardless of company policy, requirements for sealing and signing engineering documents are established by law. In California, the Professional Engineers Act contains the following language: "All civil (including structural and geotechnical) engineering plans, calculations, specifications, and reports (hereinafter referred to as "documents") shall be prepared by, or under the responsible charge of, a licensed civil engineer and shall include his or her name and license number." Electrical and mechanical engineers have similar requirements. Other states and non-USA jurisdictions probably have similar requirements, but there are probably differences too.
"Prepared by" is pretty clear. However, "under the responsible charge of" gets abused, IMHO. The California Professional Engineers Act defines "responsible charge" as follows: "The phrase “responsible charge of work” means the independent control and direction, by the use of initiative, skill, and independent judgment, of the investigation or design of professional engineering work or the direct engineering control of such projects. The phrase does not refer to the concept of financial liability." So, an engineering project manager or (on a large project) an engineering team leader working under a project manager would almost certainly meet the "responsible charge" requirements. An engineering business owner probably wouldn't unless the company was very small and the owner actually exercised "responsible charge." Being a figurehead on a project doesn't cut it, neither does being the engineer who performs the QC review.
The most egregious cases of abusing "responsible charge" that I personally know of invovled a retired engineer who would stamp and sign development plans prepared by engineering technicians for a small fee. I doubt if his "review" of their work lasted 5 minutes. This was nearly 30 years, but I'm certain it still happens today. IIRC, the retired engineer lost his license over this.
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