Non-GAAP gross profit for the quarter was $1.3 billion and grew 39% as compared to prior year. GAAP gross profit for the quarter was $1.3 billion and grew 42% as compared to prior year. GAAP gross profit includes a credit in the amount of $6.3 million in Q4 2013 and a charge in the amount of $16.1 million in Q4 2012 related to travel transaction tax litigation. These excludes the impact of the credit in Q4 2013 and the charge in Q4 2012 from non-GAAP gross profit, non-GAAP operating income, adjusted EBITDA and non-GAAP net income.
Consistent with the past practice, we exclude significant charges and credits for judgments, rulings and settlements related to travel transaction taxes, because the amount and timing of these items are unpredictable, not driven by core operating results and render comparisons with prior periods less meaningful.
Inclusion of KAYAK in our results contributed about 5 percentage points of inorganic gross profit growth for the quarter. KAYAK revenue amounted to $55 million in Q4, net of intercompany activity. Our international operations generated gross profit of $1.15 billion, which constituted an increase of 38% as compared to the prior year on both the U.S. dollar and local currency basis.
Non-GAAP gross profit for our U.S. business including KAYAK, but excluding the impact of the aforementioned travel transaction tax items, amounted to $172 million, which represented 44% growth versus prior year. Non-GAAP operating income amounted to 42.7% of gross profit for Q4 and is 106 bps lower than last year. Operating margins were impacted by 146 bps of deleverage and offline advertising, mainly related to our Booking.com TV campaigns in the U.S. and Australia and the inclusion of KAYAK offline advertising.
Q4 personnel expense includes a $12 million charge related to a payroll tax levy in the Netherlands. While there was a similar payroll tax levy in 2012, it was an accident in Q3 that year and we therefore had an unfavorable comp in Q4. Other OpEx also reflects some deleverage as we continue to invest in people, offices and IT-related expenses to support our business growth.
Online advertising expense as a percentage of gross profit is 200 bps lower than prior year. We continue to see pressure on ROIs, but to a lesser degree in Q4 than previous quarters. Much of the year-over-year improvement in this metric is due to the inclusion of KAYAK, because KAYAK spends relatively less on online advertising as a percentage of gross profit and spending by our other brands for ad placements on KAYAK is eliminated from our consolidated results. We expect KAYAK to benefit our consolidated online ad efficiency until the anniversary of the acquisition in May.
Operating margins came in 234 bps better than assumed in our guidance forecast due to gross profit over-performance, better than assumed ad efficiency and lower than forecasted other operating expenses.
Adjusted EBITDA for Q4 amounted to $578 million, which exceeded the top end of our guidance range of $540 million and represents 36% growth versus prior year. Non-GAAP net income grew by 35% and non-GAAP EPS grew by 31%, reflecting the impact of a higher fully diluted share count.