IFS has a full-time staff of about 40 researchers. IFS also employs several PhD students each year, often from universities abroad. Several research fellows from other academic institutions are affiliated to IFS and work here one or two days a week. Research associates collaborate on IFS projects on an occasional basis.

Tax professionals are sometimes called upon to participate in certain research projects which require specialist knowledge. The Tax Law Review Committee, which was created to advise on simplifying tax law, employs staff seconded from law and accountancy partnerships and from the HM Revenue and Customs.