An invariant of a group U is called a relative invariant of 16000146&_mathId=si1.gif&_user=111111111&_pii=S0747717116000146&_rdoc=1&_issn=07477171&md5=61cdc104a5bc9075defda01563887931" title="Click to view the MathML source">U⊊G if its stabilizer in G is U. The computation of Galois groups requires the construction of such invariants for permutation groups. This article reports on the constructions that are implemented in the Galois group package of magma 2.20.