Be sure to retain copies of your quote and contract. Make a note of any discussions, additions, or changes to the proposed scope, and request that your plumber documents these changes and provides you with a copy for your records.
Be sure that you receive written receipts for all payments you make. Always pay the business doing the work and not an individual person, unless the business is run by a sole trader i.e. the plumber. Be sure to get a receipt for every payment made, signed by the plumber/plumbing business.
When the work is complete, be sure you’ve received any certificates or documents for the items supplied or fitted, including warranty information.