Prepare a NZ GST101A Return from Supplier Invoices

To prepare a GST101A return from supplier invoices, NZ businesses need to do four things: extract the right purchase data from the period's source documents, apply the correct GST accounting basis, reconcile the workpaper to the ledger or cashbook, and support the purchase-side boxes on the return.

For each invoice, receipt, credit note, or adjustment record, capture the supplier, invoice date, payment date if relevant, GST-inclusive total, GST amount or GST-included signal, document type, adjustment evidence, and source file/page reference. The accounting basis then decides which rows belong in the period. Invoice-basis filers work from invoice or obligation timing. Payments-basis filers work from paid amounts. Hybrid-basis filers need enough detail to keep those treatments separate.

The purchase side of GST101A is not just one spreadsheet total. Box 11 is total purchases and expenses including GST, excluding imported goods. Box 12 is the GST calculation from Box 11 at 3/23. Box 13 is credit adjustments. Box 14 is total GST credit for purchases and expenses. A useful GST101A workpaper shows how each of those figures was built and gives the reviewer a direct path back to the source documents.

This guide focuses on the AP-side aggregation problem: turning supplier invoice PDFs, receipts, credit notes, and payment records into reviewable GST101A support. It is not a full sales-side GST guide, and it is not a screen-by-screen myIR filing walkthrough. The practical question is whether the figures entered in myIR can be traced back to a defensible purchase population.

Decide the period and basis before selecting invoices

Start with the GST period you are filing. Most small businesses file two-monthly, some file six-monthly, and larger or more complex businesses may file monthly. For the workpaper, the filing frequency matters because it defines the document population: which invoices, receipts, credit notes, and payment records are inside the return period and which belong in the next one.

The accounting basis then decides the selection rule. On invoice basis, the workpaper is driven by invoice timing and obligations. If a supplier invoice belongs to the GST period and you hold the required evidence, it can be part of the purchase-side calculation even if it has not yet been paid. On payments basis, the workpaper is driven by payments made during the period, so a dated but unpaid invoice does not automatically belong in the GST101A. Hybrid basis needs tighter discipline because some parts of the records follow invoice timing while others follow payment timing.

This is why the workpaper should carry both invoice date and payment date when the records are mixed, late, or partly reconstructed from bank transactions. A supplier invoice dated 28 February but paid on 4 March can fall into different GST periods depending on the basis. If the spreadsheet only has one date column, the reviewer has to infer the treatment later, and that is where period errors creep in.

Basis consistency is one of the first things a bookkeeper or accountant will check. Late-arriving invoices, partial payments, credit notes issued after the original invoice, and client spreadsheets that mix paid and unpaid items can all produce a GST101A figure that looks tidy but follows no single basis. The period and basis should be visible before anyone starts adding Box 11.

Build a GST101A workpaper row for every source document

A GST101A workpaper needs one row per source document or claimable transaction, not one row per supplier statement total. The row should carry enough detail to calculate the return and enough evidence for a reviewer to find the document again.

Useful columns include source file, page reference, supplier name, supplier GST number where required, document type, invoice or receipt number, invoice date, payment date, original currency, original amount, NZD amount used for GST, GST-inclusive total, GST amount or GST-included signal, net amount if shown, and a reviewer notes column. Add classification fields for credit-note sign, business/private apportionment, GST treatment, and imported-goods or overseas-supplier flags. Those fields are what separate a useful GST return workpaper from a list of totals copied out of PDFs.

Credit notes need deliberate handling. A credit note should be linked back to the supplier and source document, signed consistently, and marked as a credit note rather than treated as a negative invoice with no context. Some credit notes reduce or reverse purchase rows; others support an adjustment depending on the underlying GST treatment. Without that classification, credit notes can either inflate Box 11 by being treated as purchases or disappear from review because the spreadsheet no longer shows why the negative amount exists.

Foreign-currency supplier invoices need an NZD treatment before they are included in the GST101A figures. Keep the original currency and amount, record the NZD amount used, and note the conversion support. The timing should follow the GST basis and the records available, so a payments-basis workpaper should not silently use an invoice-date conversion if the payment record is the basis for inclusion.

Receipts and small-value documents still need enough taxable supply information to support the GST claim. This article is about aggregating records into the return, so it does not restate every buyer evidence rule. For the record requirements themselves, use the separate guide to NZ taxable supply information requirements.

For PDF invoices and scanned receipts, the key is not just extracting the GST-inclusive total. The workpaper should also preserve the source file and page reference, because the person reviewing the GST101A needs to move from a Box 11 total back to the exact supplier document without hunting through folders.

Map the workpaper to Box 11, Box 12, Box 13, and Box 14

The purchase-side boxes should be mapped before the GST101A figures are typed into myIR. The IRD GST guide says GST101A Box 11 is total purchases and expenses including GST, Box 12 is Box 11 multiplied by 3/23, Box 13 is credit adjustments, and Box 14 is total GST credit for purchases and expenses.

Box 11 starts with eligible purchases and expenses for the period, GST-inclusive, excluding imported goods. The workpaper should show which rows feed this total and which rows were excluded because they were outside the period, outside the basis rule, private, imported, exempt, or otherwise not ordinary claimable domestic purchases.

Box 12 is the GST calculation from Box 11. It is not a zero-rated purchases box, and it should not be built by adding every invoice's GST amount if that would conflict with the return's 3/23 calculation. Invoice-level GST fields are still useful because they help identify anomalies, mixed-treatment documents, and supplier records that do not support a standard GST claim.

Box 13 is where credit adjustments need attention. Bad debts written off, private-use adjustments, change-of-use adjustments, and supplier adjustment documents should be visible in the workpaper rather than buried inside a net purchase total. Credit notes should be classified by effect: some reduce or reverse purchase rows, while others support an adjustment box depending on the GST treatment. A reviewer should be able to see why each adjustment exists and whether it belongs in the current period.

Box 14 is the resulting GST credit for purchases and expenses. By the time this figure is reached, the workpaper should explain the purchase population, the calculation basis, and the adjustment support. The GST101A only receives summary numbers, but the file behind it should preserve the logic row by row.

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Flag imported goods, overseas services, and other special GST treatment

The ordinary purchase total should not absorb every supplier document just because it has a total amount. GST101A Box 11 excludes imported goods, so import invoices, customs entries, freight documents, and duty/GST paperwork should be flagged for review instead of automatically added to the domestic purchase population.

Overseas services and software subscriptions need the same caution. A non-resident supplier invoice may look like an ordinary expense in the AP folder, but the GST treatment can depend on the nature of the supply and how New Zealand GST rules apply to it. If that decision has not already been made, route the invoice through a separate check such as the non-resident supplier GST reverse charge workflow before using it in the GST101A workpaper.

Zero-rated and exempt purchases are classification issues, not a separate GST101A purchase-side box. They should be visible in the GST treatment field so the reviewer understands why the row is included, excluded, or adjusted. Property-related compulsory zero-rating is another example of a special treatment that should not be guessed from the invoice total alone.

A simple flag column prevents the workpaper from becoming overconfident. Mark domestic standard-rated purchases, imported goods, overseas services, exempt supplies, zero-rated supplies, mixed-use items, and "review required" rows separately. The final GST101A figures should be built after those flags have been checked, not before.

Reconcile Box 11 before entering the GST101A in myIR

Box 11 should tie back to the best available record set before the GST101A is filed. For a business with a proper accounting system, that might be the AP ledger, purchase report, or GST detail report. For a smaller business outside an integrated software workflow, it might be a cashbook, bank export, folder register, or expense spreadsheet. The point is to prove the workpaper population is complete enough for the basis being used.

The reconciliation target changes with the GST basis. On invoice basis, the purchase workpaper should make sense against invoices or purchase ledger activity for the period, including unpaid supplier invoices where they meet the basis and evidence requirements. On payments basis, the workpaper should make sense against cashbook or bank payments, because payment timing is what brings the purchase into the period.

Investigate differences before entering figures in myIR. Common causes include invoices dated outside the period, missing credit notes, duplicate PDF copies, supplier statements counted as invoices, imported goods left in Box 11, GST-exclusive totals used by mistake, private-use apportionment ignored, and unpaid invoices included on payments basis. A tidy spreadsheet total is not enough if the rows behind it do not match the return basis.

myIR receives summary figures. The working file explains them. If a reviewer, IRD query, or future accountant asks how Box 11 was built, the answer should be in the reconciliation notes and source-document references, not in someone's memory of the filing day.

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Use invoice extraction tools without losing the audit trail

The manual bottleneck in this workflow is rarely the 3/23 calculation. It is turning a folder of supplier invoice PDFs, scanned receipts, and credit notes into consistent workpaper rows with the same columns, signs, classification flags, and source references. If that structure is missing, the return preparation becomes a document search exercise every time someone asks where a number came from.

Software-assisted extraction is useful only if it improves that structure. A GST101A workpaper still needs source-file references, page references, document-type classification, credit-note handling, and reviewer-visible assumptions. Extracted totals with no trail back to the invoice are faster to produce but weaker to review.

Invoice Data Extraction can help where the task is to extract supplier invoice data for GST workpapers. Users upload PDFs or image files, describe the fields they want in a prompt, and download structured Excel, CSV, or JSON data. For a GST101A job, the prompt can ask for supplier name, invoice date, payment date if visible, GST-inclusive total, GST amount, document type, credit-note sign, business/private flag, GST treatment flag, and source file/page reference where available. Saved prompts can keep that structure consistent for recurring GST periods or multiple clients, while reviewers still verify the source documents before relying on the figures.

The tool does not decide New Zealand GST law, file the return, or replace accountant review. Its role is narrower and more practical: converting source documents into a spreadsheet format that can be reconciled, checked, and traced back to the underlying invoices.

Reviewer checks before the return is filed

For an accountant or bookkeeper reviewing a client GST101A, the first question is whether the workpaper follows one basis consistently. Sample rows across the period and check whether inclusion is driven by invoice date, payment date, or a documented hybrid treatment. Mixed logic is easier to find before the return is filed than after the client asks why a later payment was claimed early.

Next, test the evidence. Sample taxable supply information, confirm that source files and page references open to the right document, and check whether scans or phone photos are readable enough to support the GST claim. If a row cannot be traced back to the supplier record, it should not be treated as review-ready just because it has a total.

Then review classification and adjustments. Imported-goods flags, overseas services, exempt or zero-rated treatment, private-use apportionment, and "review required" rows should be resolved or documented. Box 13 deserves its own look: credit notes, bad debts, and change-of-use or private-use adjustments should have identifiable support rather than being accepted as a single unexplained figure.

The same source-document discipline applies to adjacent New Zealand compliance work, including when businesses prepare an NZ FBT return from supplier invoices. For GST101A, the strongest file is one where every purchase-side summary number can be traced from the return box back to a row, and from that row back to the source document.