The governing body of any county, city or town may impose, upon each person chargeable with delinquent taxes or other delinquent charges, fees to cover the administrative costs and reasonable attorney’s or collection agency’s fees actually contracted for. The attorney’s or collection agency’s fees shall not exceed 20 percent of the taxes or other charges so collected. The administrative costs shall be in addition to all penalties and interest, and shall not exceed $30 for taxes or other charges collected subsequent to 30 or more days after notice of delinquent taxes or charges pursuant to § 58.1-3919 but prior to the taking of any judgment with respect to such delinquent taxes or charges, and $35 for taxes or other charges collected subsequent to judgment. If the collection activity is to collect on a nuisance abatement lien, the fee for administrative costs shall be $150 or 25 percent of the cost, whichever is less; however, in no event shall the fee be less than $25. No tax assessment or tax bill shall be deemed delinquent and subject to the collection procedures prescribed herein during the pendency of any administrative appeal under § 58.1-3980, so long as the appeal is filed within 90 days of the date of the assessment, and for 30 days after the date of the final determination of the appeal, provided that nothing in this paragraph shall be construed to preclude the assessment or refund, following the final determination of such appeal, of such interest as otherwise may be provided by general law as to that portion of a tax bill that has remained unpaid or was overpaid during the pendency of such appeal and is determined in such appeal to be properly due and owing.