Douglas Council says the amount of unpaid rates at the end of the financial year was more than twice the previous year's figure.
A report to the local authority's executive committee revealed 99.3 per cent of rates were paid on time last year, down 0.2 per cent.
In total, £348,033 was outstanding - well up on the previous year's £148,546.
The report from the council's director of finance also said there was £472,171 in outstanding sundry debts - up from £139,476 the year before.
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