Find the non-monthly costs
Review the last 12 months for insurance renewals, MOT and servicing, memberships, school costs, birthdays, Christmas, vet costs and other predictable expenses. Add expected costs you have not paid yet.
Convert each bill into a monthly amount
If a £360 bill is due in 12 months, £30 a month funds it. If it is due in six months and you have nothing saved, the target is £60 a month. If £60 is already set aside towards that £360 bill and three contributions remain before it is due, the remaining £300 needs £100 per contribution. Count the payment opportunities you actually have. Use the Sinking Fund Planner to put several known costs into one plan. Use the Monthly Budget Calculator to check whether the contribution fits alongside essentials and required payments. Include the allowance only once.
Keep the money separate
Create labelled savings pots or a dedicated account. The aim is to stop the money looking available for everyday spending. Automate transfers just after payday.
Add a little margin
Last year's price is an estimate, not a guarantee. A modest buffer helps with price rises and avoids needing to raid the emergency fund.
Review after each bill
When the bill is paid, update next year's estimate and restart the monthly contribution immediately. If you negotiate a cheaper renewal, keep some or all of the difference going into savings.