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PLAIN INTEREST

Money and markets, explained plainly

Edition 004 14 Sep–18 Sep 2026

What hidden constraint changes what you can actually do?

An apparently simple financial choice can change once the hidden constraint is visible. Edition 4 explains five of them: access to cash, bond repricing, order execution, free float and cryptoasset tax disposals.

01 · Question

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02 · Plain answer

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03 · Picture

04 · Use it

05 · Evidence

Mon · Investing Basics · Foundation

How much cash should you keep before investing?

There is no universal cash amount to keep before investing. Start with essential monthly spending, known forthcoming costs, income stability, dependants, insurance and how quickly each pot can be reached; a common months-of-spending range is a prompt, not a rule.

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Tue · Street Smart · Market reality

Why do bond prices fall when interest rates rise?

When comparable market yields rise, an existing bond’s fixed payments become less attractive, so its market price normally falls until the overall return is competitive. The reverse usually happens when yields fall, but maturity, coupon and cash-flow timing mean bonds do not all move by the same amount.

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Wed · Trading · Active application

Stop-loss vs stop-limit: what can each fail to do?

A conventional stop prioritises getting an order into the market after its trigger, but the fill can be worse than that trigger. A stop-limit adds a price boundary, but that protection can prevent execution and leave the position open.

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Thu · Small Caps · Specialist equities

Free float explained: how many shares can really trade?

Free float is the proportion of issued shares an index methodology deems readily tradable rather than strategically or otherwise restricted. It is useful context for supply, but it is not a live count of shares offered today and it is not the same as market capitalisation or daily liquidity.

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Fri · Crypto · Alternative assets

Does swapping one cryptoasset for another trigger UK tax?

HMRC generally treats exchanging one type of cryptoasset for another as a disposal of the token given up, even when no pounds reach your bank account. A transfer of the same token between wallets you beneficially own is generally different because beneficial ownership has not changed; facts and exceptions still matter.

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Search plain-English questions…
I’m building foundationsShares, funds, risk and returns →
I want market realityOrders, spreads, custody and fees →
I’m applying the ideaPositions, sizing and exits →
I need specialist contextSmall caps and cryptoassets →