Before an assessment can be carried out, a determination is made on the validity of the request for an investigation (the complaint), specifically, whether the complaint is within the Compliance Officer's statutory remit. The Compliance Officer's powers to investigate are confined to the provisions given in the Parliamentary Standards Act 2009 (as amended by the Constitutional Reform and Governance Act 2010). If the complaint is outside the Compliance Officer's remit, an explanation will be given and, wherever possible, information will be offered to direct the complaint to the appropriate body.

If the complaint is within the Compliance Officer's remit, an assessment is carried out to consider whether there are sufficient grounds to open an investigation. At the conclusion of the assessment, the Compliance Officer may decide that there is sufficient reason to believe that a claim may have been wrongfully paid to an MP and may open an investigation. If there are insufficient grounds to do so, the compliant is closed down.

The Compliance Officer may decide not to open an investigation – even if there are grounds to do so – if it is judged that conducting an investigation would be a disproportionate course of action.

At the conclusion of an assessment, the MP, IPSA and the complainant, if applicable, are informed of the Compliance Officer's decision.

If the Compliance Officer believes that there are sufficient grounds to believe that a claim may have been wrongfully paid to an MP – and it is believed that it would not be disproportionate – an investigation will be opened. When an investigation is opened, the MP, IPSA and the complainant, if applicable, will be notified. The name of the MP under investigation and the nature of the matter investigated will be published on the Compliance Officer's website.

During the investigation, the Compliance Officer may require the MP and IPSA to provide information in the form of a written statement, or any documents relevant to the matters being investigated. The Compliance Officer may also request information from any source deemed appropriate.

Prior to the Compliance Officer producing a statement of provisional findings, the MP and IPSA have the opportunity to make representations in writing. The Compliance Officer will also give the MP the opportunity to be heard in person and to request that another person attend the hearing to represent the MP or to be asked about the matter in question. The Compliance Officer will take reasonable steps to secure that members of the public may attend the hearing, unless it appears to the Compliance Officer appropriate to impose restrictions.

An analysis of the information gathered and representations made will result in the Compliance Officer's statement of provisional findings.

Following the analysis of information gathered and representations made during the investigation, the Compliance Officer will produce a statement of provisional findings. This will detail whether the Compliance Officer believes that a claim has been wrongfully paid to an MP. It may also include details of any failures by the MP to provide information or documentation required in the process of the investigation and any findings on IPSA's role, specifically, any faults that may have led to a claim being wrongfully paid to an MP.

The Compliance Officer will send the statement of provisional findings to the MP and IPSA, who will be given the opportunity to make further representations.

If the MP accepts the Compliance Officer's provisional findings and any conditions made (e.g. to make a repayment to IPSA), the Compliance Officer may close the investigation and will not make a further statement of findings. In that case, the MP, IPSA and the complainant, if applicable, will be notified. If the MP or IPSA make further representations, the Compliance Officer will make further considerations and produce a further statement of findings.

The Compliance Officer will prepare a statement of findings in the event that further representations (in response to the statement of provisional findings) are received from the MP or from IPSA.

As with the statement of provisional findings, this will detail whether the Compliance Officer believes that a claim has been wrongfully paid to an MP. It may also include details of any failures by the MP to provide information or documentation required in the process of the investigation and any findings on IPSA's role, specifically, any faults that may have led to a claim being wrongfully paid to an MP.

The Compliance Officer will send the statement of findings to the MP, IPSA and the complainant, if applicable, and will notify them that the investigation has been concluded and that the details of the investigation are to be published.

If the Compliance Officer makes a repayment direction or imposes a penalty on an MP, the MP has a right to appeal to the First-tier Tribunal. An appeal must be brought within 28 days of the date on which the Statement of Findings was sent to the MP.