I was struck by comments made by a Judge in a QBD Planning Court decision, criticising the claimant’s Solicitors for producing over 2,000 pages of largely irrelevant material! Then, having directed the parties to put together a ‘core bundle,’ the most significant points were tucked away in paras 76 and 77 of the skeleton.
I see lots of taxpayer arguments against HMRC, and vice versa. Sadly, so many fail to highlight the clear issues at stake.
Are you arguing legal statute, or the implication of case law, or simply the issue of facts? Make it clear, assuming the person reading the document has had no prior knowledge of the dispute.
The same principles apply to any correspondence with HMRC. Make it abundantly what you are arguing.
I agree with the Judge’s comment here in relation to VAT as well as Planning:
Prolix or diffuse "grounds" and skeletons, along with excessively long bundles, impede the efficient handling of business in the Planning Court and are therefore contrary to the rationale for its establishment. Where the fault lies at the door of a claimant, other parties may incur increased costs in having to deal with such a welter of material before they can respond to the Court in a hopefully more incisive manner. Whichever party is at fault, such practices are likely to result in more time needing to be spent by the judge in pre-reading material so as to penetrate or decode the arguments being presented, the hearing may take longer, and the time needed to prepare a judgment may become extended. Consequently, a disproportionate amount of the Court's finite resources may have to be given to a case prepared in this way and diverted from other litigants waiting for their matters to be dealt with. Such practices do not comply with the overriding objective and the duties of the parties (CPR 1.1 to 1.3). They are unacceptable.
For your information, the case is Network Rail Infrastructure Ltd, R v The Secretary of State for the Environment, Food and Rural Affairs  EWHC 2259 (Admin), and there is commentary here: https://www.lawgazette.co.uk/law/thanks-a-bundle-2000-pages-of-largely-irrelevant-trial-papers-infuriate-judge/5062738.article