For a district election (including by-elections), Section 36 (4) of the Representation of the People Act 1983 states that the council may set a maximum scale of charges for the returning officer to use
The legislation states that a Returning Officer's expenses for conducting an election shall be paid by the council but if a scale is set, the expenses shall not exceed those laid down in the scale.
For parish/town council elections, Section 36 (5) states that the council may similarly set a maximum scale of charges for the returning officer to use, which the district council is responsible for paying, but which shall be repaid to the district council by the parish council for which the election is held, if the district council so requires it to be paid. It is the policy of this council that parish councils are required to pay for elections.
In Kent, the costs of conducting county, district, borough, town and parish elections are applied through the Kent Scale of Fees and Charges, which since 1998 has largely mirrored the National Scale.
You can download a copy of the scale from the downloads section of this page.