Visa applicants need to show proof of financial means to finance their trip to and stay in Germany. In some cases, the applicant may be asked to present a formal obligation (also called letter of financial support) signed by the sponsor who pays for the expenses of the visa applicant in Germany.
Your sponsor in Germany must apply for this standardized formal obligation ("Verpflichtungserklärung”) at the competent immigration office (“Ausländerbehörde” or “Ausländeramt”) which is usually situated at your sponsor’s local city administration in Germany.
Please note that only the ORIGINAL formal obligation will be accepted. A photocopy or facsimile is NOT sufficient.