What form should you use if you want to express a query in a formal manner?

Using the phrase "If you have any queries, please contact me" is the appropriate choice for expressing a query in a formal manner. This sentence is structured to invite inquiries in a professional context, demonstrating openness and willingness to provide assistance. The use of "queries" specifically denotes a formal term that is often employed in professional communication, which adds to the overall tone of formality.

In contrast, the other sentences do not convey the same level of formality or clarity regarding questions. Phrases like "If you have no questions, please let me know" and "If you are uncertain, please ignore this message" can imply a dismissive tone or lack of support, which is not conducive to a formal interaction. Meanwhile, "If you like, please talk to me" suggests a casual conversation rather than a structured query, weakening its professionality. Thus, option A stands out as the most suitable expression for soliciting queries in a formal setting.