Mergers and acquisitions (M&A), leveraged finance and capital markets are important markets for professional advisory firms such as investment banks, financial sector law firms and the ‘Big 4’ consultancies. While market totals are widely published in free sources, finding both sub-totals and lists of deals is more difficult and usually requires access to paid-for sources. In this article Ian Hunter considers the best paid-for and free sources and looks at the caveats in relying on them. In essence, he asks ‘why don't the sources agree?’ and provides a ‘jargon buster’ and a critique of sources in M&A, leveraged finance and capital markets.