You presumably know he's an officer?
The basic problem with officers is that whereas the Arnside St fire in WW2 destroyed up to 75% of service papers for enlisted men (i.e. those not commissioned officers), it destroyed all
service papers for officers. Stuff does remain for them (see http://www.nationalarchives.gov.uk/help-with-your-research/research-guides/british-army-officers-after-1913/
) but it's the ancillary papers and not everyone had such papers.
They may appear in Medal Rolls if issued with campaign medals. However, unlike enlisted men, who got theirs automatically, officers had to actually apply - and many didn't bother, so won't appear in the Medal Rolls or Medal Index Cards. (And you though the Establishment looked after its own and made the workers work for it... Nope. Other way round for Officers in regards of campaign medals!)
Any officers are normally obvious in Medal Index Card listings as they didn't have "regimental" numbers. Unless they were promoted from the ranks during the war, in which case their MICs might refer to their original rank and number, depending on the qualifying criteria for that medal.
There will be "one" place though that an officer will
appear. In the Army Lists. Some of these can be found on https://archive.org/search.php?query=%281918%29%20AND%20collection%3A%28nlsarmylists%29
- look in the indexes at the back. His appointment and promotions should also appear in the London Gazette, which is online though has a rather "challenging" interface.