Source library
Primary sources, clearly recorded.
Financial rules change. CalcSenses records where each rule came from and when it was last checked.
US calculations use official IRS and Social Security Administration material as primary sources; UK calculations use HMRC and GOV.UK publications for the 2026-27 tax year. Each calculator lists its own sources with the date they were last checked.
The US models use the IRS 2026 tax brackets and standard deductions, IRS Publication 15 for payroll and supplemental-wage rules, and verified state revenue department sources for the nine no-income-tax states. The UK models use the GOV.UK income tax, Scottish income tax and National Insurance pages for 2026-27.