Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the year ended December 31, 2023. OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from _______________ to _______________. Commission file number: 001-41899 NB BANCORP, INC. (Exact name of registrant as specified in its charter) Maryland 93-2560883 ...

Exhibit 99.1 NB Bancorp, Inc. Reports Full Year 2023 Financial Results Investor Contact ● Net income was $9.8 million for 2023, which was negatively impacted by the previously mentioned one-time expenses, most significantly the $19.1 million expense for the cash and stock contribution to the Needham Bank Charitable Foundation. ● Net income, excluding conversion and IPO-related expenses, was $34.3 million for the year ended December 31, 2023. ● Book value and tangible book value per share were $17.75 and $17 ...

Part I. Financial Information [Financial Statements](index=5&type=section&id=Item%201%2E%20Financial%20Statements) The unaudited statements show significant growth in assets, loans, and deposits, reflecting the adoption of CECL and ongoing expansion Consolidated Balance Sheet Highlights (in thousands) | Metric | September 30, 2023 | December 31, 2022 | | :--- | :--- | :--- | | Total Assets | $4,231,792 | $3,592,335 | | Loans Receivable, net | $3,683,262 | $2,990,417 | | Total Deposits | $3,436,659 | $2,886,743 | | FHLB Borrowings | $345,634 | $293,082 | | Total Equity | $365,701 | $344,065 | Consolidated Income Statement Highlights (in thousands) | Metric | Nine Months Ended Sep 30, 2023 | Nine Months Ended Sep 30, 2022 | | :--- | :--- | :--- | | Net Interest Income | $95,200 | $73,888 | | Provision for Credit Losses | $7,984 | $4,100 | | Non-Interest Income | $12,322 | $6,903 | | Net Income | $23,444 | $18,037 | - The financial statements belong to NB Financial, MHC, as the conversion to NB Bancorp, Inc was not yet complete[6](index=6&type=chunk) - The company adopted the **CECL standard (ASC 326)** on January 1, 2023, which **decreased retained earnings by $2.1 million**[17](index=17&type=chunk)[32](index=32&type=chunk) - Loans to the cannabis industry **increased significantly to $158.5 million** from $58.3 million at year-end 2022[64](index=64&type=chunk) - The company is converting from a mutual to a stock holding company, incurring **$1.8 million in deferred costs**[170](index=170&type=chunk)[171](index=171&type=chunk) - The Bank was considered **well-capitalized** with a Community Bank Leverage Ratio of **9.13%**, exceeding the minimum requirement[111](index=111&type=chunk) [Management's Discussion and Analysis (MD&A)](index=64&type=section&id=Item%202%2E%20Management's%20Discussion%20and%20Analysis%20of%20Financial%20Condition%20and%20Results%20of%20Operations) Management discusses strong loan and deposit growth, rising net interest income, and strategies for managing risk - Net loans grew by **$692.8 million**, driven by commercial real estate (+$273.4M) and commercial and industrial (+$224.3M) loans[189](index=189&type=chunk) - Deposits grew by **$549.9 million**, with core deposits increasing by **$476.3 million**, partly due to industry turmoil and branch expansion[191](index=191&type=chunk)[192](index=192&type=chunk)[193](index=193&type=chunk) - Noninterest income was boosted by a one-time **$3.5 million employee retention credit** and a **$1.9 million increase** in customer service fees[222](index=222&type=chunk)[223](index=223&type=chunk) - The provision for credit losses increased by **$3.9 million**, primarily due to significant loan portfolio growth[221](index=221&type=chunk) - The company maintains substantial liquidity from deposits and has access to **$465.8 million** from the FHLB and **$45.3 million** from the Federal Reserve[245](index=245&type=chunk) - The Bank **exceeded all regulatory capital requirements** and was categorized as well-capitalized as of September 30, 2023[251](index=251&type=chunk) Year-to-Date Performance vs. Prior Year (Nine Months Ended Sep 30) | Metric (in millions) | 2023 | 2022 | Change | % Change | | :--- | :--- | :--- | :--- | :--- | | Net Interest Income | $95.2 | $73.9 | +$21.3 | +28.8% | | Provision for Credit Losses | $8.0 | $4.1 | +$3.9 | +94.7% | | Noninterest Income | $12.3 | $6.9 | +$5.4 | +78.5% | | Noninterest Expense | $67.5 | $52.4 | +$15.2 | +29.0% | | Net Income | $23.4 | $18.0 | +$5.4 | +30.0% | Interest Rate Sensitivity Analysis (as of Sep 30, 2023) | Rate Shock (bps) | % Change in Net Interest Income | % Change in Economic Value of Equity | | :--- | :--- | :--- | | +300 | -3.5% | -2.8% | | +200 | -2.4% | -1.3% | | +100 | -0.9% | -0.2% | | -100 | 0.0% | -1.5% | | -200 | -0.7% | -5.0% | [Controls and Procedures](index=87&type=section&id=Item%204%2E%20Controls%20and%20Procedures) Management concluded that the company's disclosure controls and internal financial reporting controls were effective - Management concluded that the company's disclosure controls and procedures were **effective** as of the end of the reporting period[255](index=255&type=chunk) - **No material changes** in internal control over financial reporting occurred during the quarter[256](index=256&type=chunk) Part II. Other Information [Legal Proceedings and Other Disclosures](index=89&type=section&id=Item%201%2E%20Legal%20Proceedings%20and%20Other%20Disclosures) The company reports no material legal actions and notes its status as an emerging growth company exempts it from certain disclosures - The company is subject to various legal actions from the normal course of business, which are **not expected to have a material effect**[258](index=258&type=chunk) - As an emerging growth company, disclosures for **Risk Factors** and **Market Risk** are not required[254](index=254&type=chunk)[259](index=259&type=chunk)