There are two types of septs, the first is clansmen of the clan who were related by blood or marriage and formed separate divisions. Second, where individuals and groups who looked for, and got, the protection of the clan. These people may have been farmers, labors or servants on Mackay lands. This resulted in persons of the same surname being attached to different clans, therefore a clan had septs of various names. This is a list of names that are generally associated with Clan Mackay, only your own research will prove your link. Usa this list as a starting point.

Every person who has the same surname as the chief is deemed to be a member of the clan. Equally a person who offers allegiance to the chief is recognised as a member of the clan unless the chief decides that he will not accept that person's allegiance.

Allan, Allanson, Bain, Bayne, Kay, Key, MacAllan, MacBain, MacCaa, MacCaw, MacCay, MacGaa,  MacGaw, MacGee, MacGhee, MacGhie, MacKay, MacKee, Mackie, MacPhail, MacQue, MacQuey,  MacQuoid, MacVail, MacVain, MacVane, Morgan, Neilson, Nelson, Paul, Pole, Poleson, Pollard,  Polson, Reay, Scobie, Williamson

There is no official list of recognized septs. This is a matter for each chief to determine. But where a particular sept has traditionally been associated with a particular clan it would not be appropriate for that name to be treated by another clan chief as one of its septs.

Aberach, Abrach, Aed, Allan, Allen, Aoidh, Aue, Ave, Ay, Aye, Ayson, Bain, Baine, Baines, Bane, Bayin, Bayn, Bayne, Baynes, Baynne, Bean, Beanes, Beine, Bene, Bhaine, Cay, Caw, Coid, Coy, Eason, Easson, Esson, Eye, Faill, Fall, Ghie, Gilliam, Heth, Iye, Kae, Kay, Keay, Kee, Keye, Keyes, Keys, Kie,  M'Cay, M'aKie, M'Gy, M'Kay, M'Kee, M'Ky, Mac'Key,  Mac'Ky, Macaedh, Macaedha, Macaenghusa, Macahay, Macajee, Macai, Macakey, MacAllan, MacAllen, MacAidh, MacAiodh, MacAodha, MacAoidh, MacAth, MacAw, MacAy, MacBain, MacBayne, MacCa, MacCaa, MacCaid,  MacCaidh, MacCaoidh, MacCaw, MacCawe, MacCay, MacCee, MacCey, MacCie, Maccky, Maccoy, MacCoid, MacCoy, MacCue,MacDhia, MacEda, MacEke, MacEth, MacEthe, MacFaell, MacFail, MacFal, MacFale, MacFall, MacFaul, MacFauld, MacFaull, MacFayle, MacFoill, MacFyall, MacGaa, MacGaughey, MacGaw, MacGay, MacGe, Macgee, Macgeehee, Macghee, Macghie, MacGye,  MacHeth, MacIdh, MacIeie, Macilvain, MacIsall, MacIye, MacKa, MacKaa, MacKaay, MacKai, MacKau, MacKaw, MacKawe, MacKay, MacKaye, MacKaw, MacKCoy, MacKe, MacKeay, MacKee, Makees, MacKeiay, MacKeiy, MacKer, MacKew, MacKey, MacKhee, MacKiewicz, MacKie, MacKieson, MacKiye, MacKkcee, MacKcie,Makke, Makkee, Makkey, Makkie, Makkoy, Makky, Mca, Mcacay, Mcay, McBain, McBayne, McCa, McCaa, McCaw, McCay, McCee, McCie, McCoy, McCoye, McEy, McFall, McFaul, McGe, McGee, McGeiiee, McKee, MacKphaill, MacKy, MacKye, MacPaill, MacPaul, MacPhael, MacPhaell, MacPhail, MacPhaile, MacPhaill, MacPhale, MacPhaul, MacPhaull, MacPhayll, MacPhell, MacPhial, MacPhiel, MacQha, MacQua, MacQuade, MacQuaid, MacQuey, MacQuhae, MacQuid, MacQuiod, MacVail, MacVale, MacWhaugh, MacWhaw, MacWhey, MacWhy, MacYe, Makaw, Makay, Makca, Makcaw, Makcawe, Makcoe,Makfaill, Makfale, Makfele, Makie, Makkaw, Makkcae, Makke, Makkee, Makkey, Makkie, Makphaile, Maky, Morgan, Morgund, Murgan, Neelson, Neillsone, Neilson, Neilsone, Neilsoun, Neilsoune, Neleson, Nelesoun, Nelson, Nelsone, Nelsonne, Nelsoun, Neylsone, Nickphaile, Nielson, Nilson, Nilsone, Nilsoune, Nylson, Pal Paul, Paule, Paull, Paulson, Paulsoun, Poilson, Poilsone, Poilsoun, Pol Pole, Poleson, Pollsoun, Polson ,Polsone, Polsoun, Polsun, Polyson, Polysoun, Poulson, Quaid, Quay, Quoid, Strathnaver, Vail