Depressing experiment: install three tax reference apps, look up the same country, get three different answers, and at most one shows a date. Data quality is not one factor in the evaluation. It is the entire evaluation. - Good: every rate carries a year-effective date. Headline, small-business, and effective rates are separate fields, not one mystery number. - Good: the app names its data source and states coverage honestly. Updates come with a readable changelog. - Bad: one number per country with no date, no rate type, no source. Reviews complaining about wrong numbers the developer never answered. - My rule: if it will not tell me where its numbers come from, I assume the numbers are wrong. Has not failed me yet. A reference app is a UI on top of someone's spreadsheet, and the spreadsheet is the product. Ours is free. When the numbers become a decision, IncorpTrack registers UK and Singapore companies for $49 plus the government fee.