0001001 - Document - Cover link:presentationLink link:calculationLink link:definitionLink 1001002 - Statement - Condensed Consolidated Balance Sheets (Unaudited) link:presentationLink link:calculationLink link:definitionLink 1002003 - Statement - Condensed Consolidated Balance Sheets (Unaudited) (Parentheticals) link:presentationLink link:calculationLink link:definitionLink 1003004 - Statement - Condensed Consolidated Statements of Income (Unaudited) link:presentationLink link:calculationLink link:definitionLink 1004005 - Statement - Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) (Unaudited) link:presentationLink link:calculationLink link:definitionLink 1005006 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited) link:presentationLink link:calculationLink link:definitionLink 2101101 - Disclosure - GENERAL INFORMATION link:presentationLink link:calculationLink link:definitionLink 2202201 - Disclosure - GENERAL INFORMATION (Policies) link:presentationLink link:calculationLink link:definitionLink 2403401 - Disclosure - GENERAL INFORMATION - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 2104102 - Disclosure - REVENUE AND CERTAIN INCOME STATEMENT COMPONENTS link:presentationLink link:calculationLink link:definitionLink 2305301 - Disclosure - REVENUE AND CERTAIN INCOME STATEMENT COMPONENTS (Tables) link:presentationLink link:calculationLink link:definitionLink 2406402 - Disclosure - REVENUE AND CERTAIN INCOME STATEMENT COMPONENTS - Total Revenue by Geographic Area (Details) link:presentationLink link:calculationLink link:definitionLink 2407403 - Disclosure - REVENUE AND CERTAIN INCOME STATEMENT COMPONENTS - Cashback Rewards and Consideration (Details) link:presentationLink link:calculationLink link:definitionLink 2108103 - Disclosure - CERTAIN BALANCE SHEET COMPONENTS link:presentationLink link:calculationLink link:definitionLink 2309302 - Disclosure - CERTAIN BALANCE SHEET COMPONENTS (Tables) link:presentationLink link:calculationLink link:definitionLink 2410404 - Disclosure - CERTAIN BALANCE SHEET COMPONENTS - Schedule of Capitalized Software (Details) link:presentationLink link:calculationLink link:definitionLink 2411405 - Disclosure - CERTAIN BALANCE SHEET COMPONENTS - Schedule of Amortization Expense and Software Development Costs (Details) link:presentationLink link:calculationLink link:definitionLink 2412406 - Disclosure - CERTAIN BALANCE SHEET COMPONENTS - Property and Equipment, Net (Details) link:presentationLink link:calculationLink link:definitionLink 2413407 - Disclosure - CERTAIN BALANCE SHEET COMPONENTS - Depreciation (Details) link:presentationLink link:calculationLink link:definitionLink 2414408 - Disclosure - CERTAIN BALANCE SHEET COMPONENTS - Other Current Assets (Details) link:presentationLink link:calculationLink link:definitionLink 2415409 - Disclosure - CERTAIN BALANCE SHEET COMPONENTS - Accrued Expenses and Other Liabilities (Details) link:presentationLink link:calculationLink link:definitionLink 2116104 - Disclosure - COMMITMENTS AND CONTINGENCIES link:presentationLink link:calculationLink link:definitionLink 2317303 - Disclosure - COMMITMENTS AND CONTINGENCIES (Tables) link:presentationLink link:calculationLink link:definitionLink 2418410 - Disclosure - COMMITMENTS AND CONTINGENCIES - Summary of Lease Cost (Details) link:presentationLink link:calculationLink link:definitionLink 2419411 - Disclosure - COMMITMENTS AND CONTINGENCIES - Summary of Related to Leases (Details)(Details) link:presentationLink link:calculationLink link:definitionLink 2420412 - Disclosure - COMMITMENTS AND CONTINGENCIES - Cashflow Disclosures (Details) link:presentationLink link:calculationLink link:definitionLink 2421413 - Disclosure - COMMITMENTS AND CONTINGENCIES - Lease Maturity Schedule (Details) (Details) link:presentationLink link:calculationLink link:definitionLink 2421413 - Disclosure - COMMITMENTS AND CONTINGENCIES - Lease Maturity Schedule (Details) (Details) link:presentationLink link:calculationLink link:definitionLink 2422414 - Disclosure - COMMITMENTS AND CONTINGENCIES - Amortizing Term Mortgage (Details) link:presentationLink link:calculationLink link:definitionLink 2423415 - Disclosure - COMMITMENTS AND CONTINGENCIES - 2021 Amended Term Loan (Details) link:presentationLink link:calculationLink link:definitionLink 2424416 - Disclosure - COMMITMENTS AND CONTINGENCIES - Monthly revolving line of credit (Details) link:presentationLink link:calculationLink link:definitionLink 2425417 - Disclosure - COMMITMENTS AND CONTINGENCIES - Future aggregate annual principal payments on all long-term debt (Details) link:presentationLink link:calculationLink link:definitionLink 2425417 - Disclosure - COMMITMENTS AND CONTINGENCIES - Future aggregate annual principal payments on all long-term debt (Details) link:presentationLink link:calculationLink link:definitionLink 2426418 - Disclosure - COMMITMENTS AND CONTINGENCIES - Defined Contribution Plans (Details) link:presentationLink link:calculationLink link:definitionLink 2127105 - Disclosure - STOCK INCENTIVE PLANS link:presentationLink link:calculationLink link:definitionLink 2328304 - Disclosure - STOCK INCENTIVE PLANS (Tables) link:presentationLink link:calculationLink link:definitionLink 2429419 - Disclosure - STOCK INCENTIVE PLANS - 2009 and 2019 Stock Option Plan (Details) link:presentationLink link:calculationLink link:definitionLink 2430420 - Disclosure - STOCK INCENTIVE PLANS - 2021 Incentive Plan and Matching Plan (Details) link:presentationLink link:calculationLink link:definitionLink 2431421 - Disclosure - STOCK INCENTIVE PLANS - RSU Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 2432422 - Disclosure - STOCK INCENTIVE PLANS - RSU Rollforward (Details) link:presentationLink link:calculationLink link:definitionLink 2433423 - Disclosure - STOCK INCENTIVE PLANS - Stock Option Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 2434424 - Disclosure - STOCK INCENTIVE PLANS - Stock Option Roll-forward (Details) link:presentationLink link:calculationLink link:definitionLink 2435425 - Disclosure - STOCK INCENTIVE PLANS - Stock-Based Compensation (Details) link:presentationLink link:calculationLink link:definitionLink 2436426 - Disclosure - STOCK INCENTIVE PLANS - Stock-based Compensation Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 2137106 - Disclosure - INCOME TAXES link:presentationLink link:calculationLink link:definitionLink 2338305 - Disclosure - INCOME TAXES (Tables) link:presentationLink link:calculationLink link:definitionLink 2439427 - Disclosure - INCOME TAXES - Components of Income Tax Expense (Details) link:presentationLink link:calculationLink link:definitionLink 2440428 - Disclosure - INCOME TAXES - Reconciliation of Effective Tax Rate (Details) link:presentationLink link:calculationLink link:definitionLink 2441429 - Disclosure - INCOME TAXES - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 2142107 - Disclosure - NET (LOSS) INCOME PER SHARE link:presentationLink link:calculationLink link:definitionLink 2343306 - Disclosure - NET (LOSS) INCOME PER SHARE (Tables) link:presentationLink link:calculationLink link:definitionLink 2444430 - Disclosure - NET (LOSS) INCOME PER SHARE - Schedule of Earnings Per Share, Basic and Diluted (Details) link:presentationLink link:calculationLink link:definitionLink 2445431 - Disclosure - NET (LOSS) INCOME PER SHARE - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 2446432 - Disclosure - NET (LOSS) INCOME PER SHARE - Anti-dilutive Securities (Details) link:presentationLink link:calculationLink link:definitionLink 2147108 - Disclosure - RELATED PARTY TRANSACTIONS link:presentationLink link:calculationLink link:definitionLink 2448433 - Disclosure - RELATED PARTY TRANSACTIONS (Details) link:presentationLink link:calculationLink link:definitionLink