The Accumulated Adjustments Account (AAA) is an S-corporation equity account that tracks the corporation's cumulative income, losses, and distributions since its S election. For most S-corps that have always been S-corps (no prior C-corp history), the AAA is essentially a bookkeeping formality - all distributions come out tax-free up to the shareholder's basis and excess is capital gain. The AAA becomes critically important for S-corps that converted from C-corporations, because accumulated C-corp earnings and profits (AE&P) lurking in the S-corp can transform what looks like a capital distribution into a fully taxable dividend.
Pure S-corp (always been an S-corp, no AE&P): AAA tracks cumulative income minus losses minus distributions. Distributions are tax-free up to shareholder basis; excess is capital gain. AE&P is zero, so the ordering rules are simple. Most small business S-corps fall into this category.
Former C-corp with AE&P: If the S-corp has accumulated earnings and profits from its C-corp years (AE&P), those AE&P sit like a tax bomb inside the S-corp. Distributions come out of AAA first (tax-free to the extent of basis). Once AAA is exhausted, any distribution up to AE&P is a fully taxable dividend - ordinary income, not capital gain. Only after both AAA and AE&P are exhausted do distributions come from other accumulated adjustments (OAA) or as return of basis.
AAA starts at zero on the date of the S election (or is inherited from a prior S election). Each year, AAA is increased by the shareholder's pro-rata share of ordinary income and separately stated income items (but not tax-exempt income, which goes to the Other Adjustments Account). AAA is decreased by distributions, losses, and deductions. Losses and deductions can reduce AAA below zero, but distributions cannot reduce it below zero (IRC §1368(e)(1)(A); Treas. Reg. §1.1368-2(a)(3)). At year-end, after all income and loss allocations, distributions reduce AAA.
When an S-corp has accumulated AE&P from its C-corp years, the corporation must be careful about how distributions interact with the AAA and AE&P ordering rules. Under IRC §1368(c): distributions from an S-corp with AE&P are first applied to reduce the AAA (tax-free up to basis), then to reduce AE&P (taxable dividend), then to reduce OAA, then as return of basis (tax-free), then as capital gain. A large distribution in a year when AAA is low and AE&P is high can trigger unexpected dividend income.
The passive investment income (PII) rules create a related trap: if an S-corp with AE&P has passive investment income exceeding 25% of gross receipts for three consecutive years, the S election terminates. An S-corp that converted from a C-corp and holds investment assets must monitor passive income relative to gross receipts to avoid inadvertent termination of the S election.
Under IRC §1368(e)(3), an S-corp and its shareholders may elect to have distributions bypass AAA and come directly from AE&P first. This "bypass election" (or "distributing AE&P first election") is made annually with the consent of all affected shareholders. The bypass election is useful when the shareholders prefer to eliminate AE&P (by paying dividend tax on it now) rather than risk the passive investment income termination risk or the AE&P trap on future distributions. After AE&P is eliminated, the bypass election has no further effect - all subsequent distributions come from AAA normally.