Summary of Significant Accounting Policies	6 Months Ended
Mar. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The Company prepared the condensed consolidated financial statements in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and the requirements of the Securities and Exchange Commission (“SEC”). As permitted under those rules, certain footnotes or other financial information have been condensed or omitted. Additionally, beginning with the condensed consolidated financial statements for the three months ended December 31, 2020, the Company has reflected Interior Products as discontinued operations for all periods presented. Unless otherwise noted, amounts and disclosures throughout these Notes to Condensed Consolidated Financial Statements relate to the Company's continuing operations. Certain prior period amounts have been reclassified to conform to current period presentation. The balance sheet as of March 31, 2020 has been presented for a better understanding of the impact of seasonal fluctuations on the Company’s financial condition. In management’s opinion, the financial statements include all normal and recurring adjustments that are considered necessary for the fair presentation of the Company’s financial position and operating results. The results for the three and six months ended March 31, 2021 are not necessarily indicative of the results to be expected for the twelve months ending September 30, 2021. The three-month periods ended March 31, 2021 and 2020 had 63 and 64 business days, respectively. The six-month periods ended March 31, 2021 and 2020 had 125 and 126 business days, respectively. Beacon uses a fiscal reporting calendar which begins on October 1 and ends on September 30. The three-month period ended March 31, 2021 equates to the Company’s fiscal 2021 second quarter. These interim Condensed Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and Notes thereto contained in the Company’s fiscal year 2020 (“2020”) Annual Report on Form 10-K for the year ended September 30, 2020. Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in these consolidated financial statements and accompanying notes. Significant items subject to such estimates include accounts receivable, inventories, purchase price allocations, goodwill and intangibles, and income taxes. Assumptions made in the development of these estimates contemplate the impact of the novel coronavirus (“COVID‑19”) on the economy and the Company’s anticipated results; however, actual amounts could differ materially from these estimates. Recent Accounting Pronouncements—Adopted In June 2016, the FASB issued ASU 2016-13, “Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments.” This guidance is intended to introduce a revised approach to the recognition and measurement of credit losses, emphasizing an updated model based on expected losses rather than incurred losses. This new standard became effective for the Company on October 1, 2020. The adoption of the new standard was done using the modified-retrospective approach, through a cumulative-effect adjustment to retained earnings as of October 1, 2020. The most significant effect of the standard was an increase to the Company’s accounts receivable reserve and a corresponding retained earnings adjustment of approximately $4.3 million on October 1, 2020. In January 2017, the FASB issued ASU 2017-04, “Simplifying the Accounting for Goodwill Impairment.” This guidance is intended to introduce a simplified approach to measurement of goodwill impairment, eliminating the need for a hypothetical purchase price allocation and instead measuring impairment by the amount a reporting unit’s carrying value exceeds its fair value. This new standard became effective for the Company on October 1, 2020. The adoption of this new guidance did not have a material impact on the Company’s financial statements and related disclosures. Recent Accounting Pronouncements—Not Yet Adopted In December 2019, the FASB issued ASU 2019-12, “Income Taxes – Simplifying the Accounting for Income Taxes.” This guidance is intended to simplify the accounting for income taxes by removing certain exceptions, clarifying existing guidance and improving consistent application of the guidance. This new standard is effective for annual reporting periods, and interim reporting periods contained therein, beginning after December 15, 2020, and early adoption is permitted. The Company is currently evaluating the impact that this guidance may have on its financial statements and related disclosures. In March 2020, the FASB issued ASU 2020-04, “Reference Rate Reform (Topic 848), Facilitation of the Effects of Reference Rate Reform on Financial Reporting.” The guidance provides optional practical expedients to ease the potential burden in accounting for contract modifications and hedge accounting related to reference rate reform. In January 2021, the FASB issued ASU 2021-01, “Reference Rate Reform (Topic 848), Scope,” to clarify the scope of the guidance and reduce potential diversity in practice. The standard is effective as of March 12, 2020 through December 31, 2022. However, the standard is not applicable to contract modifications made and hedging relationships entered into or evaluated after December 31, 2022. The Company will evaluate and disclose the impact of this guidance in the period of election, as well as the nature and reason for doing so.

Summary of Significant Accounting Policies

6 Months Ended

Mar. 31, 2021

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The Company prepared the condensed consolidated financial statements in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and the requirements of the Securities and Exchange Commission (“SEC”). As permitted under those rules, certain footnotes or other financial information have been condensed or omitted. Additionally, beginning with the condensed consolidated financial statements for the three months ended December 31, 2020, the Company has reflected Interior Products as discontinued operations for all periods presented. Unless otherwise noted, amounts and disclosures throughout these Notes to Condensed Consolidated Financial Statements relate to the Company's continuing operations. Certain prior period amounts have been reclassified to conform to current period presentation. The balance sheet as of March 31, 2020 has been presented for a better understanding of the impact of seasonal fluctuations on the Company’s financial condition.

In management’s opinion, the financial statements include all normal and recurring adjustments that are considered necessary for the fair presentation of the Company’s financial position and operating results. The results for the three and six months ended March 31, 2021 are not necessarily indicative of the results to be expected for the twelve months ending September 30, 2021.

The three-month periods ended March 31, 2021 and 2020 had 63 and 64 business days, respectively. The six-month periods ended March 31, 2021 and 2020 had 125 and 126 business days, respectively. Beacon uses a fiscal reporting calendar which begins on October 1 and ends on September 30. The three-month period ended March 31, 2021 equates to the Company’s fiscal 2021 second quarter.

These interim Condensed Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and Notes thereto contained in the Company’s fiscal year 2020 (“2020”) Annual Report on Form 10-K for the year ended September 30, 2020.

Use of Estimates

The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in these consolidated financial statements and accompanying notes. Significant items subject to such estimates include accounts receivable, inventories, purchase price allocations, goodwill and intangibles, and income taxes. Assumptions made in the development of these estimates contemplate the impact of the novel coronavirus (“COVID‑19”) on the economy and the Company’s anticipated results; however, actual amounts could differ materially from these estimates.

Recent Accounting Pronouncements—Adopted

In June 2016, the FASB issued ASU 2016-13, “Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments.” This guidance is intended to introduce a revised approach to the recognition and measurement of credit losses, emphasizing an updated model based on expected losses rather than incurred losses. This new standard became effective for the

Company on October 1, 2020. The adoption of the new standard was done using the modified-retrospective approach, through a cumulative-effect adjustment to retained earnings as of October 1, 2020. The most significant effect of the standard was an increase to the Company’s accounts receivable reserve and a corresponding retained earnings adjustment of approximately $4.3 million on October 1, 2020.

In January 2017, the FASB issued ASU 2017-04, “Simplifying the Accounting for Goodwill Impairment.” This guidance is intended to introduce a simplified approach to measurement of goodwill impairment, eliminating the need for a hypothetical purchase price allocation and instead measuring impairment by the amount a reporting unit’s carrying value exceeds its fair value. This new standard became effective for the Company on October 1, 2020. The adoption of this new guidance did not have a material impact on the Company’s financial statements and related disclosures.

Recent Accounting Pronouncements—Not Yet Adopted

In December 2019, the FASB issued ASU 2019-12, “Income Taxes – Simplifying the Accounting for Income Taxes.” This guidance is intended to simplify the accounting for income taxes by removing certain exceptions, clarifying existing guidance and improving consistent application of the guidance. This new standard is effective for annual reporting periods, and interim reporting periods contained therein, beginning after December 15, 2020, and early adoption is permitted. The Company is currently evaluating the impact that this guidance may have on its financial statements and related disclosures.

In March 2020, the FASB issued ASU 2020-04, “Reference Rate Reform (Topic 848), Facilitation of the Effects of Reference Rate Reform on Financial Reporting.” The guidance provides optional practical expedients to ease the potential burden in accounting for contract modifications and hedge accounting related to reference rate reform. In January 2021, the FASB issued ASU 2021-01, “Reference Rate Reform (Topic 848), Scope,” to clarify the scope of the guidance and reduce potential diversity in practice. The standard is effective as of March 12, 2020 through December 31, 2022. However, the standard is not applicable to contract modifications made and hedging relationships entered into or evaluated after December 31, 2022. The Company will evaluate and disclose the impact of this guidance in the period of election, as well as the nature and reason for doing so.