Invoice adjustment rules clarify use of one or more credit and debit notes for supplies within a financial year. Section 34 is amended to replace singular references with plural ones: where a single tax invoice or a single credit or debit note was previously referenced, the text now refers to one or more tax invoices and to one or more credit notes for supplies made in a financial year and one or more debit notes for supplies made in a financial year, thereby permitting aggregated invoice and note-based adjustments for supplies within a financial year.