Swedish to English Social Sciences Human Resources

The text is about terms and conditions for overtime payments. A guaranteed minimum period of overtime payment applies, but if the actual time worked amounts to less than this, then the actual time worked is paid as "Övertidsersättning" and the difference between this and the minimum is classed as "utfyllnadsersättning". This is one of those cases of knowing exactly what they mean but not being able to think of the English equivalent term. Any help gratefully received. Thanks.