Can a council tax liability order be revoked by making a statutory declaration?

No

Section 14 of the Magistrates Courts Act 1980 provides that if the accused makes a statutory declaration that they were unaware of the summons or proceedings during or after a trial and serves it within 21 days, the summons and all subsequent proceedings are void. The court can accept late service of the declaration if reasonable.^[1]

A liability order gives the council the authority to use Enforcement Agents to collect a debt.^[2]

To revoke the liability order, you must get a Quashing Order. If a liability order was wrongly made, such as your address is wrong, or the sum is not lawfully owed, the council may apply to the magistrates' court to quash it. A new liability order can be issued if a lesser amount is still owed.^[3]

^{[1] Section 14 of the Magistrates Courts Act 1980
[2] Regulation 35 of the Council Tax (Administration and Enforcement) Regulations 1992
[3] Regulation 36a of the Council Tax (Administration and Enforcement) Regulations 1992}