Pronunciation: [tˈaks ˈɒn] (IPA) 
The correct spelling of the phrase "tacks on" is /tæks ɒn/. The word "tacks" is spelled with a "ck" instead of just a "k" because the "ck" spelling is used when the vowel sound before it is short. The "on" part is spelled with an "o" instead of an "a" because it follows the same rule. It is important to pay attention to spelling rules like these to ensure that the written word accurately reflects the intended pronunciation.
The phrase "tacks on" is commonly used to describe the act of adding or including something additional or extra to an existing situation, plan, or discussion. The term originates from the literal act of adding tacks or small nails onto a surface, enhancing its functionality or appearance. In a metaphorical sense, when someone "tacks on" something, they are figuratively pinning or attaching an additional element to something already established.
The phrase is often employed to convey the concept of appending an extra item, idea, task, or condition to an existing list, objective, or plan. It suggests that something is being included as an afterthought or supplement, rather than being an integral part of the original concept. For example, if a person says, "Let's go to the movies tonight, and we can tack on dinner beforehand," they are proposing to add dinner plans to the already decided movie plan as a secondary component or enhancement. Similarly, if a policy document is being revised and a new condition is being incorporated at a later stage, it can be said that the new condition is being "tacked on" to the existing policy.
Overall, "tacks on" signifies the act of adding, appending, or attaching something extra or supplementary to a previously established matter, plan, or discussion, often leaving the impression that the additional element is not an integral or fundamental part of the original concept.
