No. If your subfloor is perfectly level, an underlay is not needed. If that is not the case, we strongly recommend using a underlay. Keep in mind that they act as an additional sound barrier as well.
Better impact sound reduction (the sound towards neighbors). Without an underlay Luxury Vinyl Tiles has very LOW impact sound reduction capacity (ΔLw = +/- 4dB). Adding the basic underlay increases the impact sound reduction to 16 dB.
An underlay will eliminate the creaking noise of small dust and other particles under the floor.
Density and thickness of our underlays have been optimized for Luxury Vinyl Tiles floors. Using another underlay might result into damage of the floor and warranty will be void (see specific conditions in warranty document).
Be very careful with rubber underlays. Avoid using recycled rubber and vinyl together! If you use a rubber underlay, make sure that the underlay is suited for vinyl floors! Problems with your floor related to a non Unilin underlay voids your warranty.