Advance payment of service tax: voluntary payments allowed with intimation; excess payments may be adjusted subject to noninterpretive conditions. Provisional payment allows an assessee who cannot correctly estimate liability to request authority approval to pay provisionally. Voluntary advance payment requires intimation to the superintendent within fifteen days and disclosure in subsequent returns, with no upper limit. Excess payments may be adjusted against future liability without monetary limits, provided the excess does not arise from issues of legal interpretation, taxability, classification, valuation or exemption applicability.