How to calculate…

Predicting future salary means compounding realistic annual increases, not adding them linearly. For contracting, convert a day rate into an annual figure using billable days only, then subtract the costs an employer would otherwise absorb.

Take-home pay is your gross salary minus income tax, social contributions (National Insurance in the UK, PRSI/USC in Ireland, FICA in the US) and anything else deducted at source such as pension contributions or student loan repayments. Tax is charged in bands, so only the slice of income inside each band is taxed at that band's rate — not your whole salary.

A bonus is taxed as ordinary earnings, not at a special penalty rate. It feels heavily taxed because it lands on top of your salary, so most of it is taxed at your highest marginal rate — and payroll may treat the month as if you earned that much every month.

Your allowances are usually used up by your main job, so a second job is often taxed from the first pound at your marginal rate. The right way to work it out is to add both incomes together and tax the total, rather than treating the second job in isolation.

Student loan repayments are a percentage of income above a threshold, not a percentage of the balance. If you earn below the threshold you repay nothing, and the amount you owe has no effect on the monthly deduction.

Dividends sit on top of your other income and are taxed at their own set of rates after a small tax-free dividend allowance. Which dividend rate applies depends on the band your total income lands in.

Capital gains tax is charged on profit, not on the sale price. You take what you sold the asset for, subtract what you paid plus allowable costs, deduct your annual exemption, and tax what is left at the rate for that asset type and your income band.

A refund is simply the gap between the tax actually deducted from you and the tax you legally owed for the year. Recompute the correct liability with every allowance, credit and expense applied, then compare it to what your payslips show you paid.

Self-employed tax is charged on profit, not turnover. Deduct allowable business expenses from your income, then apply income tax plus self-employed social contributions to what remains — and remember you may also owe payments on account towards next year.

A pension pot grows from three things: what you pay in, what your employer adds, and compound investment returns over time. Small differences in contribution rate and charges compound into very large differences by retirement.

State pension is based on qualifying years of contributions, not on how much you earned. You need a minimum number of years to get anything and a full record to get the maximum, with the amount scaling pro-rata in between.

Tax relief means a pension contribution costs you less than it adds to your pot. The government tops up your contribution at your marginal rate, so a higher-rate taxpayer can add a pound to their pension for a fraction of that from take-home pay.

A repayment mortgage uses an amortisation formula: each monthly payment covers the interest accrued that month plus a slice of the capital. Early on most of the payment is interest; later most of it is capital.

Buying only wins once ownership costs plus the opportunity cost of your deposit are beaten by the equity and price growth you build. The answer is a break-even number of years, not a yes or no.

Gross yield is annual rent divided by property price. Net yield is the number that actually matters, because it subtracts every running cost — and cash-on-cash return tells you what your invested deposit is really earning.

A personal loan is amortised just like a mortgage: fixed monthly payments covering interest plus capital. Total interest depends far more on the term than most people expect — a longer term lowers the payment but raises the total cost.

Two strategies dominate: avalanche pays the highest interest rate first and costs the least, while snowball clears the smallest balance first and builds momentum. Both send every spare pound to one target while paying minimums on the rest.

Minimum payments are designed to keep you in debt: they are a small percentage of the balance, so as the balance falls the payment falls too and the end date stretches out for decades.

The 50/30/20 rule splits your take-home pay: 50% to needs, 30% to wants and 20% to savings and debt repayment. It works from net pay, not gross, which is why an accurate take-home figure matters.

Work backwards from the target and date. Divide the shortfall by the number of months, then reduce it slightly if the money will earn interest along the way.

Compound interest means you earn returns on your previous returns. The final value depends on your starting amount, regular contributions, the rate and — most powerfully — the number of years.

Inflation erodes purchasing power at a compounding rate. To see what a sum is really worth in future money, discount it by the inflation rate for each year that passes.

Compare cities by cost index, not by headline salary. Work out the equivalent gross salary that leaves you the same take-home spending power after local tax and living costs.

Net worth is everything you own minus everything you owe. It is the single clearest measure of financial progress because it captures saving, investing and debt repayment in one number.

Statutory redundancy pay is based on age, length of service and weekly pay, with a cap on the weekly figure. Contractual or enhanced schemes pay more, and part of a redundancy payment is often tax-free.

Statutory maternity pay usually starts at a percentage of your average weekly earnings for the first weeks, then drops to a flat statutory rate. Occupational schemes top this up, so check your contract before budgeting.

Statutory sick pay is a flat weekly amount paid for qualifying days of sickness, after waiting days, for a maximum number of weeks. Company sick pay schemes pay more and start sooner.

RSUs are taxed twice in different ways: as income at vesting on the market value of the shares, then as a capital gain on any growth between vesting and sale. Employers usually sell some shares at vest to cover the income tax.