From ACT Wiki
1. Financial reporting - accounting concepts.
One of a small number of fundamental accounting concepts.
Consistency requires that like items be treated consistently within each accounting period and between accounting periods.
This helps to ensure that financial information is comparable over time.
2. Cohesion - trust - comparability.
The quality of being aligned with other relevant things, and free from logical contradictions.
When statements are consistent with earlier and other statements, the level of trust toward the source of the statements increases.
Stating amounts on a consistent basis, such as an effective annual rate, makes them comparable.