Short answer：A property reference number identifies a record rather than providing a universal building-age code. Land grant, document registration, completion and occupation are different events.
Identify the relevant date
Determine which date is needed and obtain appropriate official or property documents, such as occupation evidence where applicable. Different property types have different records; a registration date need not be the completion date.
Resolve conflicting sources
Compare agency, estate, bank and documentary dates and investigate differences. Ask the lender which age basis it uses rather than deriving a loan term from an invented number-decoding rule.
Before deciding
- Record document names and provenance
- Separate land tenure from building age
- Do not infer completion year from number sequence
Sources and method
Sources support the specific rules described. Checklists and hypothetical calculations are editorial explanations, not measured market results or individual approvals.
Revision：Removed unsupported experience, case outcomes and statistics; corrected the topic-specific rules and limitations described above.
Scope：General information only, not personalised legal, tax, immigration, admissions or investment advice.