Our contribution profit grew 37% year over year to $40.7 million in the quarter.
We have signed over 140 billers so far through Q3 and had an exceptionally strong quarter for sales, driven by a large enterprise business deal.
This deal alone could add in excess of 400 basis points to our current revenue run rate when fully implemented.
We processed 70.6 million transactions in the quarter, an increase of 45% year over year, giving us an annualized run rate of over 280 million transactions.
This amount remains less than 2% of the overall domestic bill payment market of over 15 billion transactions.
In five of the six verticals that we currently focus on, utilities, insurance, financial services, telecommunications, government, and healthcare, we have less than 2% of the billers as clients, with utilities being the only one over 2%.
For example, we brought one of the largest water utilities in the US live in Q3, serving well over 1 million customers, both residential and commercial.
The implication is that we are no longer limited to only processing transactions for our 1,400-plus direct billers.
1, find and implement as many billers as possible; No.
2, constantly grow biller payment volume through digital adoption and usage; No.
3, expand the reach of IPN to process every payment from every partner as possible; No.
4, generate a long lead list of all billers that are outside of our biller-direct platform, but processed through our IPN network, and therefore, add them to our sales pipeline.
Our B2B payment volume is over $1 billion now on a run rate basis.
And similarly, our IPN network payment volume is over $1 billion as well.
In the third quarter, we processed 70.6 million transactions, representing a year-over-year increase of 44.9%.
This transaction growth drove a 30.3% increase in revenue over the same period in 2020, which resulted in revenue of $101.7 million.
I'd just like to take a moment to highlight that this is the first time the company has crossed the $100 million mark for a quarter, which is a great achievement and milestone for us.
Contribution profit for Q3 was $40.7 million, a 37.1% increase over the same period last year.
Note that the combined impact of Payveris and Finovera was less than $1 million on both revenue and contribution profit.
Adjusted gross profit for the third quarter was $32.6 million, which is an increase of 38.3% from Q3 of 2020.
Adjusted EBITDA was $5.5 million, which represents a 13.6% adjusted EBITDA margin.
The 8.6% decline in adjusted EBITDA from the second quarter of 2021 is due to the cost increases related to being a public company, increased investments in R&D and sales and marketing and some small dilutive impact from the acquisitions.
Operating expenses rose $10.9 million to $30 million for Q3 of 2021 from the same period last year.
Specifically, R&D expense increased $2.6 million or 41.7% from the third quarter in 2020 as we continue innovating with and for our customers and partners.
Sales and marketing increased $3.3 million or 41.4% as we continue to add headcount to accelerate the acquisition of new customers and partners, given the significant market opportunity and strong market position that we have and also a portion of the intangible amortization winning this sales and marketing as well.
Our GAAP net income was $0.4 million, and GAAP earnings per share for Q3 was 0.
Non-GAAP net income was $1.4 million.
Non-GAAP earnings per share was $0.01 for the quarter.
As a result of the valuation performed, we recorded $53 million of identifiable intangible assets.
And so, the related amortization decreased our GAAP net income by $933,000 and our GAAP earnings per share by $0.01 in Q3, and it will have a meaningful impact on our GAAP net income and earnings per share going forward.
As of September 30, 2021, we had $177.5 million of cash and cash equivalents on our balance sheet.
The cash decreased primarily due to the acquisitions and our share count on that date was 119.96 million shares.
Our revenue outlook for 2021 is in the range of $391 million to $393 million, which represents growth between 29.5% and 30.5% year over year.
For contribution profit, our full year outlook is between $156 million and $158 million or approximately 30% to 31%.
It's worth highlighting that our guidance now for revenue and contribution profit growth is at 30% for the full year.
For full year 2021, we also see adjusted EBITDA in the range of $26.5 million to $28 million with an adjusted EBITDA margin of approximately 17% to 18%.
We expect that our full year effective tax rate will be approximately 55%, and this is due to the discrete onetime tax items that were discussed in Q2.
On a normalized basis going forward, we would anticipate that our effective tax rate would be approximately 30%, assuming no changes to current US federal tax laws or rates.
Despite processing nearly $50 billion of processing volume in the past 12 months, I still think of it as a start-up company that truly understands the overall fintech landscape and the opportunities therein.
1, a team of industry leaders.
2, a strong, loyal and growing customer base and therefore, a line of sight to revenues in outer years.
3, a great ecosystem, leading to more biller sales and consumer adoption.
4, multiple vectors of monetization.
5, a multitrillion-dollar addressable market in the US alone.

Summary:
This transaction growth drove a 30.3% increase in revenue over the same period in 2020, which resulted in revenue of $101.7 million.
Non-GAAP earnings per share was $0.01 for the quarter.
And so, the related amortization decreased our GAAP net income by $933,000 and our GAAP earnings per share by $0.01 in Q3, and it will have a meaningful impact on our GAAP net income and earnings per share going forward.
Our revenue outlook for 2021 is in the range of $391 million to $393 million, which represents growth between 29.5% and 30.5% year over year.
For full year 2021, we also see adjusted EBITDA in the range of $26.5 million to $28 million with an adjusted EBITDA margin of approximately 17% to 18%.