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Amending an invoice

After issuing, you can still change line items, prices, or VAT — and what to do when money has changed hands

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The jobcard is the invoice, so amending the invoice means editing the jobcard. Pistonlog doesn't lock a jobcard after you've printed it — you can keep editing, and the next print reflects the changes.

Common amendments

  • Forgotten labour line — add it to the relevant job, save, print again
  • Wrong part price — edit the part's unit price, save, print again
  • Wrong customer or vehicle — change the customer / vehicle field on the jobcard, save
  • Wrong VAT rate — toggle VAT on the affected job
  • Wrong total because you missed a discount — add a discount line or adjust a labour rate

Refunds and credit notes

Pistonlog does have a credit-note model in the data layer (invoiceDocumentType enum includes credit_note, and there's an amendInvoice server flow that issues a credit note cancelling the original and creates a replacement invoice). Whether you'll touch that depends on how your invoicing is set up:

  • Most jobs (the jobcard-as-invoice flow): editing the jobcard re-prints the invoice. No credit note needed — the new print is the corrected document.
  • Formal invoices (MTD-compliant document records): once issued these are immutable. Use the credit-note amendment flow to cancel and reissue.

If a customer has already paid and you need to refund part of it:

  • Manual payments: void the original payment and record a smaller one — see Invoice lifecycle.
  • Square payments: refund directly in the Square dashboard. Pistonlog's Square webhook handles payment.created and payment.updated but not refund events, so the matching payments row in Pistonlog won't automatically flip to REFUNDED — record the situation in the jobcard's comments for the audit trail.

Audit trail

Every change to the jobcard is recorded in the activity log, so even an amended invoice has a clean history of who changed what when.

If money has changed hands

Amending an invoice that's already been paid is awkward — make sure the customer is in the loop, especially if the new total is higher. Most amendments at that stage should be matched with a written explanation in comments.

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