Every figure carries its source.
A model may help build the calculator. It never becomes the calculator.
An accountable number has a different job.
It must be reproducible from the same inputs. Its assumptions must be explicit. Its rule version must be known. Its source must be inspectable.
A number that can only be explained by the model that produced it is not a calculation. It is an opinion.
The official source comes first.
The compute layer therefore begins with the official source rather than with a model.
The published rule set is parsed and compiled into deterministic calculators. A second implementation is generated independently. The two are executed across every covered year and compared field by field, including decimal scale.
The runtime uses exact decimal arithmetic and remains offline.
Every output carries the clause, source version, source hash, assumptions, inputs, and calculation path needed to reproduce it.
The machine an organisation relies on does not ask a model to do its arithmetic.
Built and verified.
Covered by the verification set.
Field comparisons between independent implementations.
Differences in value or decimal scale.