Are you referring to county cup fees here?Grassroots Leagues comply with the Standard Code of Rules from the FA Handbook. Rule 23 (E) States:
Subject to any limits/provisions laid down by the Sanctioning Authority, Match Officials appointed under this Rule shall be paid a match fee in accordance with the Fees Tariff and travel expenses of [ ] per mile / or inclusive of travel expenses.
The Fees Tariff is set by the League but it looks like a CFA can set a level.
That was on page 499 of the 2018/19 handbook if it helps.
Are you referring to county cup fees here?