Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
overpay [əuvəˈpeɪ] vt
to overpay sb by Ь50перепла́чивать (переплати́ть*perf) кому́-н Ь50
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.