Try it all on a demo household first.

A plan says what should happen; a bank statement says what did. You can start here with no shares at all: import a statement, and the month's money in and money out are measured from what actually moved.

Measured and planned figures answer different questions, so the app keeps them apart and says which one you are looking at.

A debt costs its rate every year, whatever markets do, so paying it down earns that rate back with certainty while the rate holds, as interest you no longer pay, which is not taxed; if you deduct the debt's interest from your taxable income, paying it down returns less after tax. A savings account earns its rate before tax. An investment portfolio is the one pot with no known rate: nobody knows its return in advance.

So “pay the mortgage down, or invest?” has no automatic winner. What can be worked out is the break-even: the return an investment would need to earn, after tax, to beat paying the debt down, which is the debt's own rate. Returns are usually quoted before tax, so the app also shows that hurdle before tax, using your tax settings, labelled by how the return arrives: never sold, sold later, or paid as income. Whether a portfolio can clear that bar is your judgement.

Runway turns a vague worry into one figure: if income stopped today, how long would the household's money cover its spending? It can count cash alone, cash plus investments after the estimated tax on selling them, or everything you own less what you owe.

A runway is only as good as its inputs, so each one says where it came from, and an estimate is labelled as one.

Once money moves in and out, a simple percentage can mislead: a large deposit shortly before a rise makes the year look better than the investments did.

Modified Dietz weights each deposit and withdrawal by the days it was invested, a standard approximation of a time-weighted return that largely removes the effect of when you added or took out cash. The money-weighted return (XIRR) is the yearly rate your own money earned on its exact dates, timing included. They answer different questions, so they can differ.

Volatility, how far a price swings, is only one layer of risk. Four matter together:

• Market: broad falls take most growth assets down at once.
• Concentration: one holding or sector quietly grows to dominate.
• Liquidity: needing cash at a moment when selling is costly.
• Behaviour: stress overriding a plan made in calm.

Spreading money across asset types, sectors and regions lowers the chance that one event decides your result. A common way to organise a portfolio is core and satellite: a broad core held for the long term, with smaller, targeted positions around it. Giving each holding a stated purpose makes it easier to explain what you own, and to notice when the mix drifts.

Each kind of asset offers something different and carries its own risks:

Some of the costliest mistakes are habits rather than picks: reacting to short-term moves, adding to winners without noticing how large they have grown, reading income as growth, and letting records drift from what really happened.

A written plan, a regular review and records you trust make those habits easier to see.

Any projection rests on assumptions: what you add, what it earns, how long you wait. A useful plan shows them, so you can change one and see what moves. A projection is an estimate, not a promise.

History can test a plan too. Replaying today's holdings through past crises shows how they would have fared; it cannot say what the next fall will look like.