Assessments become liens when they are definitely known and fixed. In some cities by statute they become liens ten or more days after being confirmed and entered. By provision of law in some States an assessment of large amount (usually three to five per cent or more of the assessed value of the property) may be divided into installments payable over a period of five to ten years or more. Interest is charged on the deferred installments at five to seven per cent per annum and on due and unpaid assessments the interest ratio is increased.