By creating a solid accounting system where reports are created, and figures are analyzed directly from the system. In other words, create one source of truth. A presentation on how the solid accounting system includes proper controls that ensures accurate reporting in addition to controlling completeness and accuracy of data through segregation of duties and autoflow of data

You could provide all relevant supporting documents, like bank statements and invoices, and also offer clear explanations for any unusual or unexpected figures, ensuring clients understand the underlying reasons. One of the most important things is to indicate the source of your data whter it's rxtracted from asystem or it's provided from third party.

I’ve always found the conviction you present your output is key. Of course then backing it with the right information and techniques for clarity in your process will give that confidence and comfort to your clients.

I think having a competent team presented to a client helps in bringing confidence to them, outlining your methodology to the client and allowing the client to do a third party verification of your work helps in bringing confidence to your data.