repayment rate vs rate of payment

repayment rate and rate of payment both are nouns.

Word	Noun	Adjective	Verb	Adverb
repayment rate	Yes	No	No	No
rate of payment	Yes	No	No	No

As nouns, repayment rate and rate of payment are synonyms defined as:

repayment rate and rate of payment: the amount of money paid out per unit time

Other synonyms of repayment rate include installment rate, payment rate.

repayment rate (noun)	rate of payment (noun)
the amount of money paid out per unit time	the amount of money paid out per unit time