He seems to have been missed off the register at the right time, and added on later Herlichy lists im as an RIC offiver who joined in 1920, and ADRIC shows 1920 joining among all others on the page who joined in 1921
1898 Jan/Mar Born Kells
1901 census at Newmarket, Cork
1911 census at 9 n Newtown Street, Strabane , Tyrone, Ireland
1915 Dec 9. Commissioned 2nd Lt in R Munster Fusiliers
1917 Sep 9. Promoted Lt
1918 Mar 9. Commission in Indian Army. Lieut. Stanley Brereton Holmes, Royal Munster Fus. but to rank from 9th Sept. 1917
1918 Aug 4. 90th Punjabis. Lieut. S B. Holmes to be actg. Capt. while commdg. a Coy.
1920 Mar 13. The KING has approved the relinquishment of their probationary appointments in the Indian Army by the following officers, with effect from the dates specified: Stanley Brereton Holmes.
1920 Jun 18. R. Muns. Fus. Temp. Lt. S. B. Holmes relinquishes his commission on completion of service, 18 June 1920, and is granted the rank of Capt.
1920 Sep 9. Joined ADRIC with service no . Posted to E Coy
1921 Aug 26. Transferred to RIC as a Permanent Cadet.
1922 May 12. Pensioned. His pension was paid to a bank in London, then to 134 Clifton Pk Avenue, Belfast