How To Write A Income Statement Letter . At the top left of your letter, add a standard business header. A landlord may, for example, require a letter of employment or proof of income before renting or leasing an apartment. 16+ Proof of Letters PDF, DOC Free & Premium Templates from www.template.net Simply update the text in brackets [ ] to personalize it for your needs. Here are some examples of documents you can include with your verification letter: For example, write, “starting salary requirement ranges between $45,000 and $52,000 annually.”.