A brief index can help explain why records matter to the IRS concern. Keep copies and received evidence distinguishable from action actually completed.
Give each source a purpose
Start with the current notice and its affected period, retaining complete pages. Identify supporting material because it speaks to the point you need explained. A payment reference may clarify one relationship while another record provides different context. Keep originals and copied excerpts identifiable, naming gaps honestly. The index should make sources findable rather than assume a larger packet itself proves the correct account explanation or a completed response.
Retain later work separately
If assistance is proposed, ask which records are needed and why. Clarify scope, charges and authority before proceeding, and establish an appropriate private channel for copies. Keep later explanation, preparation and delivery evidence in their actual roles with dates and sources. A useful record of the next task helps a conversation return to the concern while formal account action and any IRS result follow their applicable processes separately.