Bexley Council is chasing millions in unpaid taxes, an investigation has found.
As the council works to become 'self-sustaibale' by 2022, a Freedom of Information (FOI) request has revealed it is still chasing thousands of accounts who have not paid up.
Council tax is often a local authority's biggest source of income, and in Bexley it was upped earlier this year to help cover budgets.
In Bexley, the council has been chasing £20m in unpaid council tax since 2012/13.
On average, in the last five years the council has had £3.3m uncollected tax a year, and newly revealed figures show that £150,000 has been written off altogether.
Last year alone nearly £30,000 was let go by the council as it was unable to recover debt.
The council has also been handing out tens of thousands of court summons as it looks crackdown on those who owe.
A council spokesman said the figures include a precept for the Greater London Authority.
The spokesman said: "If that is removed it brings the figure down to £15m.
"These figures were the amounts uncollected at the end of each year and the council continues to work hard to collect these arrears using tracing methods to find absconded debtors and takes court action to collect debt by the use of enforcement agents, attachment orders to wages and benefits, bankruptcy and charging orders on properties including orders for sale.
"Our budget setting process allows for a total collection of 98.5%. Our performance figures across London are based upon the council tax collected within financial year and we collect more than many other authorities collecting around 99% of the debt for each year.
"As an example the 2012/13 arrears of £3.4m have now reduced to £1.6m and work still continues on reducing that figure further down. "Writing off a debt is a last resort after all other efforts to find and obtain payment have been completely exhausted.
"As the council moves towards self-sufficiency, revenues from council tax are even more important as they are reinvested into key frontline services that support local residents. These services include our outstanding rated children's services, support for adults, investment in housing and keeping our streets clean."
John O'Connell, chief executive of the TaxPayers' Alliance, said paying tax must be made easier.