What a provider can genuinely commit to
A cleaning provider can commit to specifics: which areas are cleaned, with what products, at what frequency, using what method, and recorded in what way. They can commit to using colour-separated equipment, to changing cloths at defined points, and to producing a signed record of attendance and completed tasks. Those commitments are checkable, which is precisely what makes them worth having in a written proposal rather than a verbal assurance.
They can also commit to reporting. A cleaner who notices a damaged seal, a blocked drain, a pest sign or a surface that cannot be cleaned properly should tell somebody, and the arrangement should say who and how quickly. That reporting line is often more valuable to a food business than the cleaning itself, because it turns the person in the building at night into a source of early warning rather than a silent presence.
