The company's country selects the engine: US, UK, Germany, Portugal, Brazil, Mexico, Argentina and Colombia, with tables maintained by Avos.
One engine per country
The country registered on the company decides the rules. There are dedicated engines for the United States, the United Kingdom, Germany, Portugal, Brazil, Mexico, Argentina and Colombia; other countries use a generic, conservative engine that applies the rates set in the company settings.
Each engine calculates the employee side (deductions) and the employer side (charges), and the payslip shows them separately: the employee sees what left the salary, and the cost report shows what the company pays on top.
Tables kept up to date by Avos
Brackets, rates and caps live in Avos's tax-rule base, versioned by effective date. When a table changes (a contribution cap or an exemption band, for example), the following periods already use the new values with no setup on your side. Periods already paid are not recalculated.
Checking the maths
The public calculators on the site (net salary per country, vacation, bonuses and termination) use the same tables and show the steps, and the glossary explains each item. If a payroll figure looks wrong, compare it with the calculator before changing the employee record.