From Longman Dictionary of Contemporary Englishpay up phrasal verbBFLPAY FORto pay money that you owe, especially when you do not want to or you are late She refused to pay up. → paid-up → pay→ See Verb table
Examples from the Corpus
pay up• The company paid up eventually, but only after repeated threats and reminders.• If they don't pay up we will take legal action.From Longman Business Dictionarypay up phrasal verb [intransitive]FINANCE to pay money that you owe, especially because you do not want to or you are lateShe refused to pay up. → pay→ See Verb table 