we charge customers for our consulting services on a time-and-materials basis and we recognize that revenue as services are performed . we typically invoice customers annually in advance for annual and multi-year subscriptions and invoice in advance or on a time-and-materials basis for professional services . we record amounts invoiced for portions of annual subscription periods that have not occurred or services that have not been performed as deferred revenue on our consolidated balance sheet . we sell our solutions primarily through our direct sales force , which leverages our relationships with technology vendors , professional services firms and business process outsourcers . in particular , our solution integrates with sap 's erp solutions . in the fourth quarter of 2018 , sap became part of the reseller channel that we use in the ordinary course of business . sap has the ability to resell our solutions , as an sap solution-extension ( “ solex ” ) , for which we receive a percentage of the revenues . our ability to maximize the lifetime value of our customer relationships will depend , in part , on the willingness of customers to purchase additional user licenses and products from us . we rely on our sales and customer 39 success teams to support and grow our existing customers by maintaining high customer satisfaction and educating customers on the value all our products provide . the length of our sales cycle depends on the size of a potential customer and contract , as well as the type of solution or product being purchased . the sales cycle for our global enterprise customers is generally longer than that of our mid-market customers . in addition , the length of the sales cycle tends to increase for larger contracts and for more complex , strategic products like intercompany hub . as we continue to focus on increasing our average contract size and selling more strategic products , we expect our sales cycle to lengthen and become less predictable , which could cause variability in our results for any particular period . we have historically signed a high percentage of agreements with new customers , as well as renewal agreements with existing customers , in the fourth quarter of each year and usually during the last month of the quarter . this can be attributed to buying patterns typical in the software industry . as the terms of most of our customer agreements are measured in full year increments , agreements initially entered into during the fourth quarter or last month of any quarter will generally come up for renewal at that same time in subsequent years . this seasonality is reflected in our revenues , though the impact to overall annual or quarterly revenues is minimal due to the fact that we recognize subscription revenue ratably over the term of the customer contract . for the years ended december 31 , 2020 , 2019 , and 2018 , we had revenues totaling $ 351.7 million , $ 289.0 million , and $ 227.8 million , respectively , and we incurred net losses attributable to blackline , inc. of $ 46.9 million , $ 32.5 million , and $ 28.7 million , respectively . covid-19 update in december 2019 , the emergence of a novel coronavirus , or covid-19 , was reported and in march 2020 , the world health organization , or who , characterized covid-19 as a pandemic . we responded to the pandemic by creating an executive task force to monitor the covid-19 situation daily , immediately restricted non-essential travel and enabled work-from-home protocols . shortly thereafter , and in line with guidance provided by government agencies and international organizations , we restricted all travel , mandated a work-from-home policy across our global workforce , and moved all in-person customer-facing events to virtual ones . we expect these restrictions to stay in effect during the first half of 2021. we also responded with covid-19 customer-relief programs to help our community of global accounting and finance professionals in these challenging times . we have offered free access to our entire training library . we also offered the task management and reporting modules complimentary for six months to existing customers to enable a more effective remote close . in addition , we announced complimentary coaching sessions with our existing customers . we have been recognized by the stevie international business awards and the ceo world awards for our commitment to helping ensure business continuity and fostering well-being for both customers and employees in response to , and throughout the covid-19 pandemic . we have continued to see purchasing decisions being deferred due to covid-19 and a reduction on new business pipeline and large deals . moreover , we have experienced and expect to continue to experience delays in deals in emea and north america mid-market , as well as large digital transformation deals . we further expect delays in deals arising out of our sap partnership , all which will impact our customers and prospects , and our financial results for fiscal 2021. we have also seen a decrease in travel-related expenses and advertising and trade show expenses . the broader implications of the global emergence of covid-19 on our business , operating results , and overall financial performance remain uncertain and depend on certain developments , including the duration and spread of the outbreak , impact on our customers and our sales cycles , impact on our partners and employees , and impact on the economic environment and financial markets , all of which are uncertain and can not be predicted . we are conducting business as usual with certain limitations to employee travel , employee work locations , and marketing events , among other modifications . we have observed other companies taking precautionary and preemptive actions to address covid-19 , and the effects it has had and is expected to have on business and the economy . story_separator_special_tag 46 research and development replace_table_token_10_th the increase in research and development expenses for the year ended december 31 , 2020 , compared to the year ended december 31 , 2019 , was primarily due to a $ 14.9 million increase in salaries , benefits , and stock-based compensation ; a $ 2.7 million increase in computer software expenses ; and a $ 1.8 million increase in professional services expense . these increases were partially offset by a $ 5.6 million increase in capitalized software costs , which resulted in a decrease in net expenses , and a $ 0.6 million decrease in travel-related costs . the increase in salaries , benefits , and stock-based compensation was primarily driven by a 33 % increase in average headcount from the year ended december 31 , 2019 to the year ended december 31 , 2020. the increase in computer software expenses was primarily driven by our migration to the public cloud and the purchase of additional software licenses driven by an increase in average research and development headcount . the increase in professional services expense was primarily driven by external consultant fees as part of our investment in products , features , and functionality buildouts . capitalized software costs increased due to significant new enhancement initiatives related to the functionality of our solutions . travel-related expenses decreased primarily as a result of covid-19 travel restrictions . general and administrative replace_table_token_11_th the increase in general and administrative expenses for the year ended december 31 , 2020 , compared to the year ended december 31 , 2019 , was primarily due to an $ 8.8 million increase in salaries , benefits , and stock-based compensation ; $ 4.7 million of transaction-related costs ; and a $ 2.2 million increase in professional services expense . these increases were partially offset by a $ 0.8 million decrease in travel-related expenses . the increase in salaries , benefits , and stock-based compensation was primarily driven by an 18 % increase in average headcount from the year ended december 31 , 2019 to the year ended december 31 , 2020. transaction-related costs in the period related to the rimilia acquisition , which closed in october 2020. travel-related expenses decreased primarily as a result of covid-19 travel restrictions . interest income year ended december 31 , change 2020 2019 $ % ( in thousands , except percentages ) interest income $ 4,502 $ 6,128 $ ( 1,626 ) ( 27 ) % the decrease in interest income during the year ended december 31 , 2020 , compared to the year ended december 31 , 2019 , was primarily due to a decrease in average interest rates , partially offset by interest earned on higher cash balances in the year ended december 31 , 2020 , compared to the year ended december 31 , 2019 . 47 interest expense year ended december 31 , change 2020 2019 $ % ( in thousands , except percentages ) interest expense $ 23,311 $ 8,650 $ 14,661 169 % the increase in interest expense during the year ended december 31 , 2020 , compared to the year ended december 31 , 2019 , was primarily due to increased amortization of the debt discount on the notes . the notes were issued in the third quarter of 2019 and , as such , there was less amortization in 2019 as compared to a full year in 2020. the increase was also , to a lesser extent , related to increased interest accrued during the period on the outstanding balance on the notes in the year ended december 31 , 2020 , compared to the year ended december 31 , 2019. provision for income taxes replace_table_token_12_th we are subject to federal and state income taxes in the united states and taxes in foreign jurisdictions . for the year ended december 31 , 2020 , our annual estimated effective tax rate differed from the u.s. federal statutory rate of 21 % primarily as a result of state taxes , foreign taxes , and changes in our valuation allowance for domestic income taxes . for the years ended december 31 , 2020 and 2019 , we recorded $ 0.7 million and $ 1.7 million in income tax expense , respectively . the decrease in income tax expense for the year ended december 31 , 2020 , compared to the year ended december 31 , 2019 , was attributable to 2020 tax benefits associated with our international operations . for the year ended december 31 , 2020 , we continued to maintain a full valuation allowance on our u.s. federal and state net deferred tax assets as it was more likely than not that those deferred tax assets will not be realized . liquidity and capital resources at december 31 , 2020 , our principal sources of liquidity were an aggregate of $ 542.6 million of cash and cash equivalents and marketable securities , which primarily consist of short-term , investment-grade u.s. treasury securities , corporate bonds , and commercial paper . in october 2020 , we completed the acquisition of rimilia and paid $ 121.4 million . we had $ 500.0 million aggregate principal amount of notes outstanding at december 31 , 2020. during the quarter ended december 31 , 2020 , the stock price condition allowing holders of the notes to convert was met . as a result , holders have the option to convert their notes at any time during the calendar quarter ending march 31 , 2021. we have the ability to settle the notes in cash , shares of our common stock , or a combination of cash and shares of our common stock at our election . from january 1 , 2021 , through the date of this filing , we have not received any conversion requests for our notes . it is our current intent to settle any such conversions through combination settlement , which involves repayment of the principal portion in

net cash provided by operating activities our net loss and cash flows from operating activities are significantly influenced by our investments in headcount and infrastructure to support anticipated growth . in recent periods , our net loss has generally been significantly greater than our use of cash for operating activities due to our subscription-based revenue model in which billings occur in advance of revenue recognition , as well as the substantial amount of non-cash charges which we incur . non-cash charges primarily include depreciation and amortization , stock-based compensation , non-cash lease expense , amortization of debt discount and issuance costs , and deferred taxes . for the year ended december 31 , 2020 , cash provided by operations was $ 54.7 million , resulting from net non-cash expenses of $ 97.5 million , partially offset by our net loss of $ 39.4 million and net cash flow used as a result of changes in operating assets and liabilities of $ 3.4 million . the $ 3.4 million of net cash flows used as a result of changes in our operating assets and liabilities reflected the following : a $ 12.4 million increase in other assets ; a $ 5.7 million increase in accounts receivable ; a $ 5.3 million increase in prepaid expenses and other current assets ; a $ 5.0 million decrease in operating lease liabilities ; and a $ 4.4 million decrease in accounts payable . these changes in our operating assets and liabilities were partially offset by the following : a $ 26.4 million increase in deferred revenue as a result of the growth of our customer and user bases ; and a $ 3.1 million increase in accrued expenses and other current liabilities . for the year ended december 31 , 2019 , cash provided by operations was $ 29.7 million , resulting from net non-cash expenses of $ 68.2 million , partially offset by our net loss of $ 32.1 million and net cash flow used as a result of changes in operating assets and liabilities of $ 6.3 million .


 Write a concise suspicious activity report of the following text delimited by triple backquotes. Return your response as a formal report which covers the key points highlighting the location,dates,entity names and account holder information in chronological order of the text.
     ```net cash provided by operating activities our net loss and cash flows from operating activities are significantly influenced by our investments in headcount and infrastructure to support anticipated growth . in recent periods , our net loss has generally been significantly greater than our use of cash for operating activities due to our subscription-based revenue model in which billings occur in advance of revenue recognition , as well as the substantial amount of non-cash charges which we incur . non-cash charges primarily include depreciation and amortization , stock-based compensation , non-cash lease expense , amortization of debt discount and issuance costs , and deferred taxes . for the year ended december 31 , 2020 , cash provided by operations was $ 54.7 million , resulting from net non-cash expenses of $ 97.5 million , partially offset by our net loss of $ 39.4 million and net cash flow used as a result of changes in operating assets and liabilities of $ 3.4 million . the $ 3.4 million of net cash flows used as a result of changes in our operating assets and liabilities reflected the following : a $ 12.4 million increase in other assets ; a $ 5.7 million increase in accounts receivable ; a $ 5.3 million increase in prepaid expenses and other current assets ; a $ 5.0 million decrease in operating lease liabilities ; and a $ 4.4 million decrease in accounts payable . these changes in our operating assets and liabilities were partially offset by the following : a $ 26.4 million increase in deferred revenue as a result of the growth of our customer and user bases ; and a $ 3.1 million increase in accrued expenses and other current liabilities . for the year ended december 31 , 2019 , cash provided by operations was $ 29.7 million , resulting from net non-cash expenses of $ 68.2 million , partially offset by our net loss of $ 32.1 million and net cash flow used as a result of changes in operating assets and liabilities of $ 6.3 million .
```    
 Suspicious Activity Report : we charge customers for our consulting services on a time-and-materials basis and we recognize that revenue as services are performed . we typically invoice customers annually in advance for annual and multi-year subscriptions and invoice in advance or on a time-and-materials basis for professional services . we record amounts invoiced for portions of annual subscription periods that have not occurred or services that have not been performed as deferred revenue on our consolidated balance sheet . we sell our solutions primarily through our direct sales force , which leverages our relationships with technology vendors , professional services firms and business process outsourcers . in particular , our solution integrates with sap 's erp solutions . in the fourth quarter of 2018 , sap became part of the reseller channel that we use in the ordinary course of business . sap has the ability to resell our solutions , as an sap solution-extension ( “ solex ” ) , for which we receive a percentage of the revenues . our ability to maximize the lifetime value of our customer relationships will depend , in part , on the willingness of customers to purchase additional user licenses and products from us . we rely on our sales and customer 39 success teams to support and grow our existing customers by maintaining high customer satisfaction and educating customers on the value all our products provide . the length of our sales cycle depends on the size of a potential customer and contract , as well as the type of solution or product being purchased . the sales cycle for our global enterprise customers is generally longer than that of our mid-market customers . in addition , the length of the sales cycle tends to increase for larger contracts and for more complex , strategic products like intercompany hub . as we continue to focus on increasing our average contract size and selling more strategic products , we expect our sales cycle to lengthen and become less predictable , which could cause variability in our results for any particular period . we have historically signed a high percentage of agreements with new customers , as well as renewal agreements with existing customers , in the fourth quarter of each year and usually during the last month of the quarter . this can be attributed to buying patterns typical in the software industry . as the terms of most of our customer agreements are measured in full year increments , agreements initially entered into during the fourth quarter or last month of any quarter will generally come up for renewal at that same time in subsequent years . this seasonality is reflected in our revenues , though the impact to overall annual or quarterly revenues is minimal due to the fact that we recognize subscription revenue ratably over the term of the customer contract . for the years ended december 31 , 2020 , 2019 , and 2018 , we had revenues totaling $ 351.7 million , $ 289.0 million , and $ 227.8 million , respectively , and we incurred net losses attributable to blackline , inc. of $ 46.9 million , $ 32.5 million , and $ 28.7 million , respectively . covid-19 update in december 2019 , the emergence of a novel coronavirus , or covid-19 , was reported and in march 2020 , the world health organization , or who , characterized covid-19 as a pandemic . we responded to the pandemic by creating an executive task force to monitor the covid-19 situation daily , immediately restricted non-essential travel and enabled work-from-home protocols . shortly thereafter , and in line with guidance provided by government agencies and international organizations , we restricted all travel , mandated a work-from-home policy across our global workforce , and moved all in-person customer-facing events to virtual ones . we expect these restrictions to stay in effect during the first half of 2021. we also responded with covid-19 customer-relief programs to help our community of global accounting and finance professionals in these challenging times . we have offered free access to our entire training library . we also offered the task management and reporting modules complimentary for six months to existing customers to enable a more effective remote close . in addition , we announced complimentary coaching sessions with our existing customers . we have been recognized by the stevie international business awards and the ceo world awards for our commitment to helping ensure business continuity and fostering well-being for both customers and employees in response to , and throughout the covid-19 pandemic . we have continued to see purchasing decisions being deferred due to covid-19 and a reduction on new business pipeline and large deals . moreover , we have experienced and expect to continue to experience delays in deals in emea and north america mid-market , as well as large digital transformation deals . we further expect delays in deals arising out of our sap partnership , all which will impact our customers and prospects , and our financial results for fiscal 2021. we have also seen a decrease in travel-related expenses and advertising and trade show expenses . the broader implications of the global emergence of covid-19 on our business , operating results , and overall financial performance remain uncertain and depend on certain developments , including the duration and spread of the outbreak , impact on our customers and our sales cycles , impact on our partners and employees , and impact on the economic environment and financial markets , all of which are uncertain and can not be predicted . we are conducting business as usual with certain limitations to employee travel , employee work locations , and marketing events , among other modifications . we have observed other companies taking precautionary and preemptive actions to address covid-19 , and the effects it has had and is expected to have on business and the economy . story_separator_special_tag 46 research and development replace_table_token_10_th the increase in research and development expenses for the year ended december 31 , 2020 , compared to the year ended december 31 , 2019 , was primarily due to a $ 14.9 million increase in salaries , benefits , and stock-based compensation ; a $ 2.7 million increase in computer software expenses ; and a $ 1.8 million increase in professional services expense . these increases were partially offset by a $ 5.6 million increase in capitalized software costs , which resulted in a decrease in net expenses , and a $ 0.6 million decrease in travel-related costs . the increase in salaries , benefits , and stock-based compensation was primarily driven by a 33 % increase in average headcount from the year ended december 31 , 2019 to the year ended december 31 , 2020. the increase in computer software expenses was primarily driven by our migration to the public cloud and the purchase of additional software licenses driven by an increase in average research and development headcount . the increase in professional services expense was primarily driven by external consultant fees as part of our investment in products , features , and functionality buildouts . capitalized software costs increased due to significant new enhancement initiatives related to the functionality of our solutions . travel-related expenses decreased primarily as a result of covid-19 travel restrictions . general and administrative replace_table_token_11_th the increase in general and administrative expenses for the year ended december 31 , 2020 , compared to the year ended december 31 , 2019 , was primarily due to an $ 8.8 million increase in salaries , benefits , and stock-based compensation ; $ 4.7 million of transaction-related costs ; and a $ 2.2 million increase in professional services expense . these increases were partially offset by a $ 0.8 million decrease in travel-related expenses . the increase in salaries , benefits , and stock-based compensation was primarily driven by an 18 % increase in average headcount from the year ended december 31 , 2019 to the year ended december 31 , 2020. transaction-related costs in the period related to the rimilia acquisition , which closed in october 2020. travel-related expenses decreased primarily as a result of covid-19 travel restrictions . interest income year ended december 31 , change 2020 2019 $ % ( in thousands , except percentages ) interest income $ 4,502 $ 6,128 $ ( 1,626 ) ( 27 ) % the decrease in interest income during the year ended december 31 , 2020 , compared to the year ended december 31 , 2019 , was primarily due to a decrease in average interest rates , partially offset by interest earned on higher cash balances in the year ended december 31 , 2020 , compared to the year ended december 31 , 2019 . 47 interest expense year ended december 31 , change 2020 2019 $ % ( in thousands , except percentages ) interest expense $ 23,311 $ 8,650 $ 14,661 169 % the increase in interest expense during the year ended december 31 , 2020 , compared to the year ended december 31 , 2019 , was primarily due to increased amortization of the debt discount on the notes . the notes were issued in the third quarter of 2019 and , as such , there was less amortization in 2019 as compared to a full year in 2020. the increase was also , to a lesser extent , related to increased interest accrued during the period on the outstanding balance on the notes in the year ended december 31 , 2020 , compared to the year ended december 31 , 2019. provision for income taxes replace_table_token_12_th we are subject to federal and state income taxes in the united states and taxes in foreign jurisdictions . for the year ended december 31 , 2020 , our annual estimated effective tax rate differed from the u.s. federal statutory rate of 21 % primarily as a result of state taxes , foreign taxes , and changes in our valuation allowance for domestic income taxes . for the years ended december 31 , 2020 and 2019 , we recorded $ 0.7 million and $ 1.7 million in income tax expense , respectively . the decrease in income tax expense for the year ended december 31 , 2020 , compared to the year ended december 31 , 2019 , was attributable to 2020 tax benefits associated with our international operations . for the year ended december 31 , 2020 , we continued to maintain a full valuation allowance on our u.s. federal and state net deferred tax assets as it was more likely than not that those deferred tax assets will not be realized . liquidity and capital resources at december 31 , 2020 , our principal sources of liquidity were an aggregate of $ 542.6 million of cash and cash equivalents and marketable securities , which primarily consist of short-term , investment-grade u.s. treasury securities , corporate bonds , and commercial paper . in october 2020 , we completed the acquisition of rimilia and paid $ 121.4 million . we had $ 500.0 million aggregate principal amount of notes outstanding at december 31 , 2020. during the quarter ended december 31 , 2020 , the stock price condition allowing holders of the notes to convert was met . as a result , holders have the option to convert their notes at any time during the calendar quarter ending march 31 , 2021. we have the ability to settle the notes in cash , shares of our common stock , or a combination of cash and shares of our common stock at our election . from january 1 , 2021 , through the date of this filing , we have not received any conversion requests for our notes . it is our current intent to settle any such conversions through combination settlement , which involves repayment of the principal portion in

