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flat rate UK US noun [C]
► a rate that is fixed at a particular level that does not change, however much work is done or however much a service is used: »
The only exceptions to this flat rate are calls to 0800 and 0808 numbers.
»They were the first to introduce flat-rate pricing for texts and mobile broadband.
»a flat-rate contribution
► FINANCE a rate of interest on a loan that is charged on the original amount that was borrowed, not on the amount of debt that is still to be paid back: »
If you borrow £5,000 on a 6% flat rate, you will still pay 6% interest on £5,000 in the last year, when most of the loan has already been repaid.
► a rate that is the same for everyone: »
Employees will contribute a flat rate of £15 monthly.
Financial and business terms. 2012.