Write the change against the original agreement
Identify the original scope and the item being added, removed, or substituted. Ask why the change is needed and whether there are alternatives. If a different product is proposed, record its model or specification rather than saying only “equivalent.” Keep any warranty difference visible in the decision.
The change should state the added or reduced cost and any effect on the payment schedule. Clarify whether the stated amount is fixed for that scope or still an estimate. Do not sign a blank approval or rely on an undefined promise that the difference will be worked out afterward.
Confirm who has authority
In a rental, condo, or jointly managed property, the person present may not be the person permitted to approve the expense. Contact the responsible owner or manager. The provider should know who can authorize the changed work before opening another area or ordering equipment.
Save the evidence and revised result
Keep a photo or written description of the condition if it can be obtained safely. Attach the change record to the original proposal and final invoice. Ask whether permits, inspections, or another trade's work are affected.
The Illinois Attorney General's home-repair resources provide broader consumer guidance. This page is not a legal determination of a contract dispute. Its practical purpose is to make the revised agreement understandable before a newly discovered condition becomes an unexplained invoice line.