Which of the following details must be confirmed by an original source before inserting it in the data sheet?

The legal property description must be confirmed by an original source because it is a critical detail that defines the legal standing of the property within land registry systems. This description is essential for verifying ownership, boundaries, and tax assessments, and it typically includes elements such as the lot number, plan number, and any easements or restrictions affecting the property. Relying on incorrect or outdated information could result in legal challenges or disputes over property rights, making it imperative to validate this information against official documentation.

In contrast, while other details like the age of appliances, garden size, rental equipment details, basement condition, and year of renovation are also important, they can often be verified through visual inspection or reliance on the seller's disclosures rather than needing authoritative documentation. Hence, the legal property description stands out as requiring confirmation from a reliable and original source.