The attitude in this sentence, which is an indicative declarative sentence, is one of assertion of fact. The sense of attitude in communication is a function of mood in grammar. In order to change the sense of attitude currently expressed in the indicative mood of "Your error on your tax for will result in a penalty to you," it will be necessary to change the mood. Of course, this quote gives no indication as to whether this is an advance warning such as may be seen in tax form instructions or a statement following the actual commission of an error.
In either case, one possible mood change that will change the sense of attitude is a change to a mood indicating probability or improbability, certainty or uncertainty, through structuring the sentence as a conditional. As a first conditional, the sentence would be paraphrased as, "If you have an error on your tax form, it will result in a penalty to you" (i.e., if / present simple verb / will + base verb ). As a third conditional, it would be paraphrased as, "If you had an error on your tax form, it would have resulted in a penalty to you" (i.e., if / past perfect verb / would have + past participle verb). A second conditional wouldn't do for a mood since it requires a simple past tense in the if-clause: if / simple past tense / would + base verb (e.g., "If I won the game, I would buy a boat."). The quoted sentence could also be paraphrased in the subjunctive mood as, "If there were to be an error on your tax form, it would result in a penalty to you."
The conditional mood indicates the probability or certainty of an occurrence happening and takes the form of a condition expressed as an if-clause (e.g., "If pigs had wings") followed by a result clause (e.g., "I will/would/would have laughed."). The subjunctive mood expresses a type of condition that is wishful or doubtful and is used to express a doubt, regret, demand, request, proposal, etc. It is often, but not always, expressed as an if-clause (e.g., "If I were president") followed by the expression of the wish, doubt, etc. (e.g., "... I would wish to resign"; "I wish I were able to dance better").