A structure and design procedure for complementary N-band IIR filterbanks is proposed. The N-band filterbank has a tree-like structure with cascaded 2-band complementary filters and related all-pass filters. No inverse filterbank is needed and the subband signals are simply added to re-construct the time-domain signal. While no perfect reconstruction is achieved, the filterbank impulse response is all-pass with a well-behaved group delay. The proposed filterbank is suitable for delay-critical audio processing applications. The computational complexity of the proposed IIR filterbanks is significantly lower than that of corresponding FIR filterbanks.