What can a lawyer not do concerning fees charged to a client?

A lawyer cannot collect an unreasonable fee or expenses as it directly violates the ABA Model Rules of Professional Conduct. Rule 1.5 specifically states that a lawyer's fees must be reasonable and takes into account several factors, including the time and labor required, the novelty and difficulty of the questions involved, and the skill required to perform the legal service properly. Charging an unreasonable fee undermines the integrity of the legal profession and can exploit clients, particularly vulnerable ones who may not fully understand the complexities of legal fees.

Reasonable fees are established to ensure that clients are treated fairly and to promote transparency in legal billing practices. Therefore, collecting fees that exceed what is considered reasonable can lead to disciplinary action against the lawyer, including potential sanctions.

In contrast, the other choices present different scenarios that may not directly breach the rules. For example, charging fees based on a client's financial need might be acceptable if it is agreed upon and disclosed properly. Contingent fees can be valid under certain conditions, and adjusting fees might be permissible if clients are informed adequately. These aspects require clear communication and proper agreements but do not inherently violate the primary ethical standards regarding fee collection as set by Rule 1.5.