Thank you, Jack. I'll cover the financial highlights for the First Quarter and our outlook for the Second Quarter and full year 2021.
On the income statement, total revenue for the First Quarter was $74 million, representing growth of 9%. Recurring revenue from subscription and support grew 11% year-over-year to $70.7 million. Professional Services revenue was $3 million for the quarter, a 20% year-over-year decline, which was expected due to the COVID 19 travel impacts. Overall, gross margin was 67% during the First Quarter and our product gross margin remained strong at 68% or 72% when adding back depreciation and amortization, which we refer to as cash gross margin. Operating expenses excluding acquisition related expenses, depreciation, amortization and stock compensation were $30.4 million for the First Quarter or 41% of total revenue, all generally as expected. Also, acquisition-related expenses were approximately $9.6 million in the First Quarter and of course these acquisition related expenses will continue as a result of our renewed acquisition activity. I will note that $1.2 million of this Q1 expenses related to an office lease exit from last year's acquisition. Acquisition-related expenses are generally 52% to 60% of acquired annual revenue run rate and varies from acquisition-to-acquisition depending on uncontrollable factors such as geographic location. Generally for each acquisition, 45% to 50% of these transaction and transformation expenses are incurred within the first 3 months and then taper down rapidly until complete by the acquisitions First Anniversary.
Our First Quarter 2021 adjusted EBITDA was $22.8 million or 31% of total revenue, down 7% compared to $24.6 million or 36% of total revenue for the First Quarter of 2020.
As expected, adjusted EBITDA was lower due to our increased go-to-market investments compared to last year on the cash flow.
For the First Quarter of 2021, GAAP operating cash flow was $12.5 million and free-cash flow was $12.2 million even with $9.6 million of acquisition-related expenses in Q1.
We also had some positive changes in some of the working capital accounts like collections on accounts receivable. 2021 free cash flow should be over $30 million and possibly over $40 million depending upon the size and timing of future acquisition, so we are focused on generating substantial GAAP operating cash flow and free cash flow even after acquisition-related expenses.
So for the balance sheet, this ongoing free cash flow generation is an addition to our existing liquidity of $246.7 million comprised of approximately 186.7 million of cash on our balance sheet as of March 31, 2021 and our $60 million undrawn revolver. This ongoing cash flow generation existing available capital and expanding our credit facility while maintaining net debt leverage of up to a maximum of around 4.0 times should allow for self-sustained growth without dependency on the equity markets. I should note that our net debt leverage is currently at around 3.5 times based on the midpoint of our 2021 adjusted EBITDA guide. With regard to income taxes, I will note that Upland currently has approximately $356 million of total tax NOL carry-forwards and of these, we estimate that approximately 215 million will be available for utilization prior to expiration.
As of March 31, 2021 we had outstanding net debt of approximately 345.2 million after factoring in the $186.7 million of cash in our balance sheet. I note that principal payments on our term debt are 1% per year or about $5.4 million per year.
With the remaining balance maturing in August of 2026, the interest rate on our outstanding term debt is locked at 5.4% making our annual cash interest payments approximately $30 million at our current debt level.
Additionally, I will point out that our term debt has no financial covenants on current borrowings.
Now for guidance, for the quarter ended June 30, 2021, Upland expects reported total revenue to be between $73 and $77 million including subscription and support revenue between $70.2 and $73.2 million for growth in recurring revenue of 6% at the midpoint over the quarter ended June 30, 2020.
Second Quarter 2021, adjusted EBITDA is expected to be between $22 and $24 million.
For an adjusted EBITDA margin of 31% at the midpoint, representing a reduction of 3% at the midpoint over the quarter ended June 30, 2020, reflecting our incremental investment and our go-to-market activities.
For the full year ending December 31, 2021, Upland expects reported total revenue to be between $299 and $311 million including subscription and support revenue between $285.3 and $295.3 million.
For growth in recurring revenue of 5% at the midpoint over the year-ended December 31, 2020. Full year 2021, adjusted EBITDA is expected to be between $94.4 and $100.4 million for an adjusted EBITDA margin of 32% at the midpoint, representing a reduction of 3% at the midpoint over the year ended December 31, 2020, again reflecting our incremental investments in go-to-market activities.
So with that, I'll pass the call back over to Jack.