Your tenancy agreement governs how much rent you pay every month and when you have to pay it. Usually, rent is due on the third working day of the month. If you are unable to pay your rent on this date, you fall behind on your payments and accrue what are known as rent arrears.
If you realise that you will not be able to pay your rent on time, let your landlord know. Contact social services and the Jobcenter as soon as you can and enquire about financial support.
If you have registered as unemployed and receive unemployment benefit 2 (Arbeitslosengeld 2, or ALG 2) for accommodation and heating, the Jobcenter is the right place to contact. If you receive cost of living benefit or basic welfare for the elderly, or are unable to pay your rent because you have a low income, please contact social services.