Common mistakes include forgetting irregular costs such as car repairs, birthdays, annual insurance and Christmas, or using gross rather than take-home income. Some people underestimate everyday spending, leave out debt repayments and subscriptions, or set targets so strict that the budget becomes difficult to follow. Check your bank statements and bills from the past three months, include a small amount for unexpected costs, and review the plan regularly. If your income varies or debts are difficult to manage, consider free guidance from a UK debt charity or check the MoneyHelper budgeting guidance.