The Valuation Office Agency (VOA) – which gives the Government property valuations and advice – received 250 challenges from Northumberland residents over their Council Tax bill in 2020/21 – down from 340 the year before.
Of the challenges which were resolved, 60 resulted in the tax bill decreasing.
Nationally, 40,620 challenges were launched – down from 43,650 in 2019/20 and, of the 38,070 resolved disputes, 11,670 (31%) resulted in the Council Tax band being decreased.
Homes are given a Council Tax valuation band by the VOA based on its value in April 1991.
Think tank Bright Blue said a rise in the proportion of successful challenges shows that the system has "long passed its sell-by date".
Joseph Silke, communications officer Bright Blue, said: “The banding system devised three decades ago disproportionately burdens those with more modest means.
“If the Government wants to level up, council tax should be replaced with a fairer annual proportional property tax.”
The Institute of Economics Affairs said the council tax system is too vulnerable to "arbitrary" challenges by individual households which can affect a lot of people.
Andy Mayer, chief operating officer, said: "Often one person’s appeal triggers the revaluation of a whole group of homes, leading to further appeals.”
The Ministry of Housing, Communities and Local Government said it has no plans to reform Council Tax.
A spokeswoman added: “We are providing councils with £670m to enable them to continue reducing council tax bills this year for those least able to pay.”