How We Build and Check Our Tools

Who is responsible

Every tool and guide is researched, checked and maintained by Sayed Muqtada Hussain, the founder of ToolsForPro. Each guide shows the date it was last updated, and each tool links back to this page.

Where the numbers come from

We use the body that publishes a rule, not another website's summary of it. The main sources are:

• US tax and pay: IRS publications and annual inflation adjustments (brackets, standard deduction, EITC, Child Tax Credit, 401(k) limits) and the Social Security Administration (wage base).
• US mortgages and inflation: Freddie Mac's weekly Primary Mortgage Market Survey and the Bureau of Labor Statistics CPI-U index.
• UK: HMRC and GOV.UK (Stamp Duty Land Tax bands, Income Tax, National Insurance, student loans, State Pension) and UCAS for tariff points.
• Pakistan: the Finance Act and FBR withholding schedules (salary tax, sections 236C and 236K), provincial stamp acts and board notifications, NEPRA tariff decisions for electricity bills, and the official admission formulas published by each university, the PMDC and the IBCC.
• Islamic finance: the nisab and shares used for zakat, fitrana, khums and inheritance follow established fiqh rulings, and our guides say which school or authority a figure comes from where opinions differ.
• Health: standard published formulas (for example WHO BMI categories and Naegele's rule for due dates).

Guides link to or name the source for the figures they quote.

How every number is checked

1. The rule is read from the source and written into the calculator.
2. Worked examples are run through the calculator, then checked by hand against the source.
3. Edge cases are tested (thresholds, minimums, zero and very large inputs) before a page goes live.
4. Pages are checked on mobile and desktop before publishing.

We use software, including AI writing and coding assistants, to help draft text and build tools. Software does not decide what is published: every rate, formula and example is checked against the source before it goes live.

How often we update

We keep a calendar of the dates when rules change and update the affected tools on or soon after those dates:

• Weekly: the US mortgage rate used by the home affordability calculator (Freddie Mac, Thursdays).
• Monthly: US inflation data after each CPI release.
• Yearly: US tax brackets and 401(k) limits (October–November), the UK Budget and new tax year (April), and Pakistan's federal and provincial budgets (June–July).
• As announced: mid-year changes such as new electricity tariffs, stamp duty changes or admission formula updates.

When a rate changes, the "updated" date on the page changes with it.

Corrections

If you find a wrong rate, a broken calculation or an outdated rule, please tell us and include the source if you have it. We check every report, and confirmed mistakes are usually fixed within a day.

Independence and advertising

No company pays for a tool or a result. Advertising and any future affiliate links are kept separate from the calculations, are clearly labelled, and never change an answer. See the About page for how the site is funded.

Limits

Our tools give careful estimates, not personal advice. Your own situation can include rules a general calculator cannot know about. For a filing, a contract, a medical decision or a religious obligation, confirm with a qualified professional or scholar. See the Disclaimer.