Terms of reference are the instructions a surveyor agrees with the client before the survey. The IIMS Code of Conduct asks members to obtain clear terms of reference from the client and confine their report to them. ITIC advises identifying the client on day one, getting clear instructions, and defining at the outset the precise extent of the work and what's excluded.
What a surveyor checks
That the terms name the client, the purpose, the scope and exclusions, the fee, and who may rely on the report. ITIC adds a statement that the report is only for the intended recipient and use. See terms of engagement for the full list.
In the report
"Instructions: pre-purchase survey for the named client only, as agreed in writing before the survey. Rig inspected from deck level only; engine not opened up; gas system not tested, as excluded in the terms of engagement."