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Corrections are the most useful thing you can send.
Reporting a mistake in the figures
The arithmetic is tested, but assumptions can still be wrong or misleading. If a number looks off, the fastest way to get it fixed is to send the link from your address bar — it contains every input, so the exact scenario can be reproduced — along with what you expected and why.
Suggesting a comparison
The engine is not specific to property. If there is a tradeoff you keep working out by hand — paying down a mortgage against investing, buying a car outright against financing it, bonds against a term deposit — it is worth asking for. Knowing which ones people actually need decides what gets built next.
What this is not
Nobody here can tell you whether to buy a particular property, and questions about your own circumstances cannot be answered. The about page explains what the tool does and does not account for, and anything beyond that needs a qualified adviser who knows your position.