The upcomping 5th generation (5G) of mobile communication system aims to support multiple new services and use cases towards a flexible and unified connectivity. In order to meet the corresponding requirements, Universal-Filtered Orthogonal Frequency-Division Multiplexing (UF-OFDM) was proposed to replace the existing waveform since it combines the advantages related to OFDM with better spectral properties and with improved robustness against time-frequency misalignments. However, its main drawback resides in the computational complexity of the transmitter reaching up to 200 times that of OFDM if no simplification is applied. While still of high complexity, most efficient simplification techniques significantly compromise the achieved spectral confinement through signal approximations. In this context, a novel low-complexity UF-OFDM transmitter without any signal quality loss is proposed. For small subband sizes, the complexity becomes comparable to OFDM regardless of the number of allocated subbands. Furthermore, the proposed transmitter architecture is flexible and can be easily adapted to support OFDM modulation.