The son of Elijah and Isabel Watt Sells was born on March 1, 1858, in Muscatine, Iowa. He received his preliminary education in the public schools of Iowa. He attended Baker University but he did not complete the requirements for a degree. He received an honorary Master of Arts degree from Baker University (1909) and an honorary Doctor of Commercial Science degree from New York University (1916). He was certified as a CPA in 1896 (New York).
His earlier business experience was with the railroads. In 1874 he joined the Leavenworth, Lawrence & Galveston Railroad, later part of the Santa Fe System, in Baldwin, Kansas as an assistant station agent. He later worked in the general office of the Kansas City, Fort Scott & Memphis Railroad. He remained with divisions of the Chicago, Burlington & Quincy System until 1879. For the next fourteen years he worked with railroads in various parts of the country. He was cashier, paymaster and bookkeeper for the Chicago, Clinton, Dubuque & Minnesota Railroad in Dubuque, Iowa (1879-81); chief clerk for comptroller, Oregon Railway and Navigation Company, Portland, Oregon (1881-84); auditor, Pacific Coast Railway, San Louis Obispo, California (1884); auditor, Oregon Improvement Company, San Francisco, California (1884-87); assistant comptroller, Fort Scoff & Memphis Railroad (1887-88); secretary and auditor, The Colorado Midland Railway Company, part of the Atchison, Topeka & Santa Fe System (1888-93). In 1893 he became the chief clerk for the general auditor of the Atchison, Topeka and Santa Fe Railroad. He was an honorary member of the American Association of Railway Accounting Officers. In June 1893, he left the railroads when he and Mr. Charles Waldo Haskins were selected by the Joint Commission ("Dockery Commission") of the Fifty-third Congress to study various aspects of the Executive Departments, Bureaus, Divisions, and other government establishments at the National Capital to determine if any modifications could be implemented that would be more efficient and economical without injury to the public service. This was the most extensive and important undertaking of the kind in the history of the country and the first instance of the employment of professional accountants in such a major undertaking by the federal government. Many of their recommendations for reorganizing the accounting system of the U. S. government were adopted by Congress and others were promptly put into effect by executive order.
Upon completion of this assignment in 1895, he and Mr. Haskins formed the firm Haskins & Sells; the first major auditing firm in this country to be established by American rather than British accountants. In 1903 he became senior administrator of the firm, after the death of Mr. Haskins. This position he held at his death. He served two terms as president of the AICPA (1906-08). He served on the AICPA's Council (1916-22) and Executive Committee (1916-22). He was also chairman of its Committee on Budget and Finance (1916-22), and a member of its Special Committee on Endowment (1917-23). He also held professional membership in many state societies of CPAs including those of Illinois, Maryland, Missouri, New York State, Pennsylvania, and Ohio. He was instrumental in the formation of the School of Commerce, Accounts, and Finance at New York University in 1900. He made important contributions to the accounting literature. Among the articles he authored were "Corporate Management Compared with Government Control," "Publicity of Financial Affairs of Corporations," "The Natural Business Year for Inventories and Fiscal Closings," "The Accounting Profession - Its Demands and its Future," and "A Plan for International Peace." This last article, published in The Journal of Accountancy in its February 1915 issue, was comprehensive and farsighted. In 1923 his friends established the Elijah Watt Sells Scholarship Fund, which provides the awards made by the AICPA to those candidates sitting for the CPA examinations who receive the highest scores.
He married Mabel Graveson April 24,1884; they had two children. In his leisure time he enjoyed tennis, horseback riding, and farming. He died on March 19, 1924 at the age of 66.