In 812, he was forced to pay 25,000 solidi in tribute to Charlemagne. In 814, he pledged an annual tribute of 7,000 solidi to Louis the Pious. These promises, however, were never kept and his successor, Sico, made the same empty guarantees. The Beneventans were independent in practice and by the end of the ninth century would not even recognise Frankish overlordship. Grimoald was assassinated in 817 by a complot of nobles vying for his throne.