How these calculators work, what they assume, and where they mislead
What each of the seven tools assumes, which sources it uses, when it was last verified, and the cases where its answer will mislead you.
Informational only — not tax or legal advice
This content is for informational purposes only and does not constitute legal, tax, or financial advice. Always consult with qualified professionals familiar with your specific circumstances before making any decisions.
A calculator is a set of assumptions with a number on the end. Some don’t tell you what theirs are. The ones here — Tax Residency Days Tracker, FX Reality Check, Multi-Currency Invoice Generator, Get-Paid-From-Abroad Decoder, Visa-for-Freelancers Comparator, Cost-of-Living Equivalency, Tax Treaty Lookup — have a number, and they publish the assumptions behind it: the sources, the last verification date, and the cases where the answer will mislead you.
Three commitments, in the order that matters:
- Sources are named. Every externally maintained value links to the source that sets it, not a paraphrase.
- Pages are dated. Every record carries a verified date, and the recheck rounds that changed it are published.
- Limitations are published. Each tool names what it does not do — and where it can be wrong — before it names what it does.
That third one is the part some calculators skip. A tool that cannot state its own limits has not been understood by the person who built it.
How the tools are built
The architecture is the point:
- Everything runs in the browser. Nothing you enter into a calculator is transmitted to a server or stored anywhere. The input fields, the calculation, the output document — all of it happens on your device.
- No accounts, and no analytics on what you compute. There is no server to leak, because nothing reaches one. There is no way for the site to see what you are calculating, which is also why it cannot help you if something is wrong — the trade is explicit.
- What that means practically: the privacy claim is structural, not policy-based. It holds because the data never moves, not because the operator promises not to read it.
On analytics: the site runs two, both for aggregate traffic only — Cloudflare Web Analytics 1 and Plausible 2. They measure page views and referrers across the site. Neither is wired to the calculators, so neither can see what you compute. What each product collects is described in its own documentation, linked above, and what this site does with it is in the privacy policy. Optional feedback, data-rights requests, email requests and affiliate links are separate flows, documented separately.
Aggregate page-view analytics, both products named, neither connected to the calculators — that is what the site observes.
The seven tools
Each block follows the same shape: what it computes, what it is based on, when it was last verified, what it deliberately does not do, and — first — where it can mislead you.
Residency Days Tracker
Where it can mislead you: it uses the midnight-presence day convention; countries that apply part-day counting will produce a different figure. It counts; it does not determine tax residency.
What it computes: calendar days from user-entered date ranges, against configured tax-year windows, with threshold markers.
What it’s based on: the day arithmetic is implemented by the site, not supplied by an external provider; country names and codes follow ISO 3166 3; each country record links to that country’s own tax authority or legislation.
Last verified: 2026-06-07
What it deliberately does not do: apply a day-counting convention as a universal test, run treaty tie-breakers, or decide residency — the 183-day marker is presented only as a threshold used in some rules, not a determination.
Read first: The 183-day rule is not the rule
FX Reality Check
Where it can mislead you: provider fees vary by country, corridor, funding method, account plan, amount, time and promotions; a published reference rate is not necessarily the rate available to the user; some providers disclose fees but not the full spread; intermediary and receiving-bank charges may not be known in advance.
What it computes: a comparison of a reference exchange rate against provider fees and margins stored in the site’s provider dataset, showing the arithmetic behind the comparison.
What it’s based on: a named reference rate source with its timestamp displayed; the European Central Bank’s euro reference rates, which the ECB states are published for information purposes and strongly discourages using for transaction purposes 4. Provider rows link to the exact pricing or fee page used, not merely the provider homepage 4.
Last verified: 2026-07-15
What it deliberately does not do: describe any provider as universally “best”; reference rates are not executable quotes.
Read first: What happens to your money across borders
Multi-Currency Invoice Generator
Where it can mislead you: mandatory invoice fields differ by country, transaction, customer type, tax status and e-invoicing regime; the user chooses tax rates and treatment; a regular-expression check confirms only that text resembles an expected format — it does not prove a tax number exists, belongs to the named business, or is active; locally stored draft data remains on the device and may be accessible to other users of the same browser profile.
What it computes: a formatted invoice document, created in the browser from user-entered information.
What it’s based on: pdf-lib, the PDF library the site deploys (5); ISO 4217 currency codes 6.
Last verified: 2026-06-15
What it deliberately does not do: determine tax, choose VAT or GST treatment, verify a tax ID against a registry, or guarantee the invoice satisfies local legal or e-invoicing rules.
Read first: The €1,000 test
Get-Paid-From-Abroad Decoder
Where it can mislead you: published headline prices may omit add-ons, deposits, FX, payroll, benefits, local fees, taxes or bespoke quotations; EOR suitability depends on the worker, client, work location, role, duration and local employment rules; entity-formation cost does not represent total operating, accounting, banking, substance, tax or closure cost; the scoring model reflects choices made by the site — the factors and weights are published.
What it computes: a rule-based decision aid that maps user-selected circumstances to payment, EOR or entity-formation paths, displaying cost bands and questions to investigate.
What it’s based on: published pricing pages for EOR and entity-formation providers (Deel, Remote, Oyster, Firstbase, Stripe Atlas, Xolo, Osome); banking and FX paths reuse the exact source register from the FX Reality Check rather than a second, inconsistent set of fees.
Last verified: 2026-06-09
What it deliberately does not do: provide personalised legal, tax, employment or financial advice.
Read first: What a company in another country does — and doesn’t do — for you
Visa-for-Freelancers Comparator
Where it can mislead you: immigration rules can change without notice; a programme’s marketing name may not match its legal permit category; official pages may omit consulate-specific implementation details; immigration permission and tax residence are separate questions; e-Residency is a digital identity card, not a residence or immigration status, and must not be grouped as if it were a visa.
What it computes: a summary of selected facts from government sources for a defined set of visa or residence pathways.
What it’s based on: the exact government page stored in each production visa record; the source pack lists starting points for auditing the planned set.
Last verified: 2026-08-20
What it deliberately does not do: determine eligibility, guarantee approval, or establish tax treatment.
Read first: Tax residency, explained
Cost-of-Living Equivalency
Where it can mislead you: city averages hide neighbourhood, household, housing-quality and lifestyle differences; crowdsourced observations can be sparse, stale or unrepresentative; exchange rates move more frequently than the underlying datasets; rent often dominates the result and is highly sensitive to assumptions; taxes, healthcare, childcare, schooling, deposits, moving costs and visa costs may be excluded.
What it computes: purchasing-power differences for selected categories, applying a transparent equivalency formula to a bundled city dataset and user-selected lifestyle assumptions.
What it’s based on: the Numbeo cost-of-living database; redistribution rights for that data must be checked against the Numbeo terms of use, and the site does not publish or redistribute scraped Numbeo data unless its use is permitted by the applicable terms or licence 78.
Last verified: 2026-08-01
What it deliberately does not do: predict an individual household’s actual spending.
Read first: Where you live, where your company is, where your money sits
Double Tax Treaty Lookup
Where it can mislead you: “no record” in the site’s dataset is not proof that no treaty exists; a signed treaty may not yet be in force; multilateral instrument (MLI)s, exchanges of notes, protocols, termination, suspension or replacement may alter the text; different taxes, persons, entities, income types, territories and effective dates may be covered differently; official texts may exist in multiple languages, and translations may not be authoritative.
What it computes: whether the site’s curated dataset contains a treaty record for a selected pair, with a link to source material, and displays signing and in-force dates stored in that record.
What it’s based on: the OECD tax treaties topic and Model Tax Convention, the OECD Multilateral Instrument matching database, and each treaty party’s official authority or treaty collection 9.
What it deliberately does not do: interpret the treaty, apply tie-breakers, calculate withholding, or determine that a person is covered.
Read first: Read your tax treaty in ten minutes
How the data is maintained
Every record carries the date it was last verified, and that date is shown on the page. No fixed re-check cycle is promised: records are re-verified as sources change and as errors are reported, and the date moves when they are.
Publishing the dates is the proof, and it costs nothing: a stale date is visible to anyone who looks, which is exactly why it is shown.
The data freshness table below is generated from production at publication time — coverage counts are not copied from planning documents, and each lastVerified date is reported exactly as stored:
| Tool | Production dataset or code path | Coverage count | lastVerified |
|---|---|---|---|
| Residency tracker | src/content/countries/ | 28 countries | 2026-06-07 |
| FX reality check | src/content/providers/ + rate endpoint | 8 providers | 2026-07-15 |
| Invoice generator | src/lib/tax-id.ts + PDF code | 27 tax-ID patterns | 2026-06-15 |
| Payment decoder | src/data/decoder-tree.ts + provider data | 27 countries × 4 income types × 3 invoicing frequencies × 3 delivery types | 2026-06-09 |
| Visa comparator | src/content/visas/ | 13 pathways | 2026-08-20 |
| Cost of living | src/content/cities/ | 26 cities | 2026-08-01 |
| Treaty lookup | src/content/treaties/ | 106 records | 2026-08-20 |
Every record carries a visible “last verified” date, and corrections reported to the address in the footer are made and noted.
What this site is not
Stated plainly, without hedging:
- Not a tax adviser, not a law firm, not qualified. The author holds no professional credentials, and the site says so openly. It does not advise, assess, review or opine on anyone’s situation.
- Not a substitute for professional input on anything that matters. The tools count, compare and look up. They never determine residency, calculate tax owed, recommend structures, or apply tie-breakers algorithmically.
- Not neutral about money. There are affiliate relationships — here is the list. Some links are affiliate links; if a qualifying action is completed, the site may receive compensation. Affiliate eligibility, commissions and terms are controlled by the partner or network and can change. Compensation does not change the calculator’s arithmetic or ranking. At the time of writing there is exactly one programme with a live tracked link: SafetyWing, a nomad health-insurance provider. It is unrelated to money transfer, tax or company formation, and none of the providers compared in the tools is an affiliate partner.
- Not comprehensive. Seven tools cover a fraction of the questions. The coverage counts above are exact, not rounded up.
This section reads as weakness and functions as strength. It is not softened, and it should not be.
Where this goes next
One demand test, framed as a question, not a pitch: which of these would be worth paying for — saved multi-year day history, alerts before you cross a threshold, or an exportable record for your accountant? Reply and say which. No prices, no dates, no commitment — just the question, asked so the next tool is the one people actually want.
What you can do with this
That is the full picture: seven tools, their sources, their dates, and their named limits. What you can do with it: use the tools, check the sources, and treat the output as a starting point — not a conclusion. Nothing here is tax, legal or financial advice; where the money is real, a qualified professional is the right next step.