In the case of a service relationship that is not an employment relationship within the meaning of section 622, termination is permissible
1. if the remuneration is assessed by days, on any day with effect for the end of the following day;
2. if the remuneration is assessed by weeks, at the latest on the first working day of a week with effect for the end of the following Saturday;
3. if the remuneration is assessed by months, at the latest by the fifteenth of one month with effect for the end of the calendar month;
4. if the remuneration is assessed by quarters or longer periods of time, observing a notice period of six weeks, with effect for the end of a calendar quarter;
5. if the remuneration is not assessed by time periods, at any time; in the case of a service relationship that completely or mainly takes up the economic activity pursued by the person obliged; however, a notice period of two weeks is to be observed.