Dispute an invoice payment and late payment of invoices


The SA Government is committed to being open and transparent about its payment performance

Getting started

The "How to" section provides information related to:

  • How to check a late payment interest amount

  • How to dispute penalty interest on an invoice

  • How Late Payment Interest (penalty interest) is calculated and more...

Additional resources about the creation, submission and processing of invoices can be found in the links below: 

How to

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How can I check a late payment interest amount?

Businesses can calculate the late payment interest they may be entitled to, using the Late payment calculator.

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How will a business know if penalty interest has been paid?

The Remittance Advice will show the interest paid as a separate line item (in most cases).

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How is late payment interest calculated?

The late payment interest amount must be calculated with the following formula: I = ND x (IA x PIR) / 365


  • I is the interest payable to the business
  • ND is equal to the number of days that the invoice is paid late (i.e. interest starts to apply from the 31st day after the Agency Invoice Received Date)
  • IA is the value of the invoice (GST exclusive)
  • PIR is the prescribed interest rate applying on the first day of the month in which the default period ends. The prescribed interest rate is the Reserve Bank Cash Rate for the applicable month plus 5%.
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Liability for Late Payment Interest – what if it is Shared Service SA's fault?

  • Shared Services SA endeavours to process every transaction correctly and meet agreed service levels. Whilst the processes and systems that have been established should minimise instances where our action/inaction results in a public authority paying interest on an overdue invoice, it is recognised that we will make mistakes and errors from time to time.

  • In accordance with the Service Level Determinations established with each in-scope public authority, Shared Services SA is not financially liable for any errors made in the delivery of its services to public authorities.

What happens if an invoice is not correctly rendered (e.g. incorrectly addressed, missing a Purchase Order number, etc.)
  • Businesses are required to correctly render invoices for payment. See answer to: (What is the definition of a correctly rendered invoice?) for further details.

  • If the invoice is not rendered correctly then it can be considered to be in dispute.

  • Whilst the invoice is in dispute, payment cannot be made.

  • No late payment liability will be incurred during the time an invoice is in dispute (providing the reason for the dispute is consistent with the requirements of the Act and/or Treasurer's Instruction 11.)

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What happens if there is a dispute as to whether late payment interest should or should not be paid against a particular invoice?

  • A business may lodge a dispute with a public authority regarding a number of matters such as: the amount of interest paid, the length of time an invoice was with the public authority before payment (i.e. the Agency Received Date) or why a particular invoice was disputed.

  • In the event that there is a disagreement between a business and a public authority over the matter of late payment interest, the business should seek to resolve the matter with the public authority in the first instance. Where Shared Services SA provides an accounts payable service to a public authority, disputes can be lodged with Shared Services SA in the first instance.

  • Should a business not be satisfied with the response provided, it may escalate the dispute to the Chief Executive of the applicable public authority. Should the business still not be satisfied, the matter can be referred to the Small Business Commissioner. Under the Act, the Small Business Commissioner has the authority to make determinations as to whether interest should be paid to a business, based on the particular circumstances of each case.

  • Section 7 of the Act allows for the Small Business Commissioner to specify procedures and requirements to resolve disputes which may arise between a public authority and a business.

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