A normal month, written down
List what leaves your account in a typical month: food shopping, travel, phone, energy top-ups, everything small. The difference between income and those essentials is the honest space a monthly payment can live in.
The 80% test
Whatever space you find, plan at 80% of it. If £10 a month is spare, take an £8 plan. The missing 20% absorbs the month the car needs tyres — and that is the month that decides whether a plan survives.
Monthly beats 'I'll manage'
Plans built on 'I'll manage' fail in month nine. Plans built on a written month rarely fail at all. Five minutes with a notepad is the highest-value five minutes in this whole process.
Questions people ask
What if my income is irregular?
Budget on your worst recent month, not your best. If the plan still fits at 80% of that, it is safe.
Should I take a shorter plan to pay less overall?
Only if the bigger monthly amount still fits at the 80% test. A cheaper plan you miss is more expensive than a longer plan you keep.
Do you have a calculator?
The homepage has one — slide the monthly amount and months to see the shape of a year.
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