If you are searching "BAS record-keeping requirements," you are usually trying to confirm two things: what has to be kept, and for how long. The ATO requires you to keep records that explain every transaction reported on the BAS, across GST, PAYG withholding, fuel tax credits, and any other reported amount. In practice that means tax invoices, receipts, bank statements, import documentation, fuel tax credit calculations, and the working papers that show how each figure was worked out. Most GST records must be kept for five years, but the clock is more precise than most people assume, and record-keeping is not really about storage at all. It is about being able to show how a BAS figure was produced, because a number you cannot explain is a number you cannot defend.
How long, and the invoice rules that actually get claims denied
The five-year period sounds simple and has one trap in it. It runs from the later of when you prepared or obtained the record, or when the transaction it relates to was completed, and you must keep records long enough to cover the period of review for any assessment that uses them. That "whichever is later" wording matters, because if a BAS is lodged late, the retention period effectively stretches past a flat five years from the invoice date. Disposing of records exactly five years after the transaction can leave you short if the related BAS went in late or was amended.
The bigger exposure is not retention length, it is the tax invoice rules for claiming GST credits, and there are two thresholds worth knowing precisely. You must hold a valid tax invoice to claim a GST credit on a purchase of more than $82.50 including GST. Below that, a receipt or equivalent record showing the supplier, date, description and amount is enough. At $1,000 including GST or more, the tax invoice must also identify the buyer by name or ABN. Miss a required field on a high-value invoice and the ATO can deny the entire input tax credit, which turns a coding question into real unrecoverable money. Imports are the exception that catches firms out: you do not need a tax invoice to claim GST credits on imported goods, but you must hold the Department of Home Affairs documentation showing the GST actually paid at the border. So "we reconciled it" is never the evidence. The invoice, or in the import case the customs document, is.
Why traceability is the real requirement
The most common weakness in a firm's records is not missing paperwork, it is missing linkage. The transaction sits in the ledger, the receipt exists somewhere, but nothing connects the coding decision to the document that justifies it. That gap is invisible until it matters, and then it matters a lot: when GST was only partially claimed, when a private-use percentage was applied, when an adjustment was made after reconciliation, or when a BAS is amended later and the ATO expects the records to explain both the original figure and the correction. This is why bank feed data alone is never sufficient evidence. A reconciled account proves money moved, not that the GST treatment was correct or that a valid invoice exists behind it. If GST on purchases is claimed with no valid tax invoice, or import GST is reported with no customs documentation, the reconciliation does nothing to protect the claim.
How to make records defensible, not just complete
The ATO's expectation is not perfection, it is traceability: every figure on the Activity Statement should trace back to a supporting record and be explainable on its own. The practical way to get there is to attach the supporting document to the transaction inside the accounting file, so the invoice, the coding decision, and the amount live together rather than in three separate places nobody can reconcile under audit pressure. Keep the invoices, import documents, and working papers organised and linked as the quarter goes, not reconstructed at BAS time when the context has faded. BAS record-keeping is not about surviving five years of storage. It is about any single figure being able to explain itself the moment someone asks. Build that linkage into the transaction layer, and the BAS becomes defensible instead of a box of documents you hope adds up.
