付账 is the standard way to say 'pay the bill.' Synonyms include 买单 (mǎidān, casual/Southern) and 结账 (jiézhàng, settle the bill). In restaurants, 买单 is the most common spoken form.
culture
Fighting over who pays the bill (抢着付账 qiǎngzhe fùzhàng) is a well-known Chinese social ritual. Offering to pay shows generosity and respect.
