While it’s possible to install vinyl flooring without underlayment, it’s not always recommended. Underlayment provides extra cushioning, sound insulation, and can help smooth out minor subfloor imperfections. For vinyl planks or tiles with pre-attached backing, underlayment may not be necessary. However, if your subfloor is uneven or you want additional comfort and noise reduction, installing underlayment is a good idea. Always check manufacturer guidelines for the best installation practices.