A broadband polarisation-insensitive terahertz (THz) metamaterial absorber (MMA) is presented in this paper. The MMA consists of a simple planar structure as a unit cell and an optically transparent indium tin oxide (ITO) ground plane, both are separated by a 50μm dielectric substrate. We designed three combinations of MMA here, which are ITO–polyimide–ITO, ITO–polyethylene terephthalate (PET)–ITO and ITO–silicon dioxide (SiO 2) –ITO for the same planar structure. By changing the substrate of the structure, the resonant frequency and bandwidth of the absorber structure can be varied. The numerical simulation of the absorber shows that the absorptivity is > 96 % for all three substrates. Polyimide, PET and SiO 2 based absorbers demonstrated the bandwidth of 0.558 THz, 0.603 THz and 0.658 THz with covered broadband frequency range of 0.4254–0.9829 THz, 0.457–1.16 THz and 0.511–1.169 THz respectively. ITO–PET–ITO absorber structure produced optical transparency. These bandwidths are compatible and convenient for electronic sources in the terahertz region. This study also provides applications in THz sensing and imaging, communication and detection systems. © 2020, Indian Academy of Sciences.