Efrain Rivera
Senior Vice President, Chief Financial Officer at Paychex
Thanks, John, and good morning to all of you. I hope you're indoors on this smokey Thursday. I thought we were past it, but not quite. I'd like to remind everyone that today's commentary will contain forward-looking statements, refer to the customary disclosures that we make.
Let me start by providing a summary of our fourth quarter financial results, talk about full year results and then finish with a review of our fiscal 2024 outlook. Before I start, I also wanted to add that joining us in the room today this morning is Bob Schrader, VP of Finance and IR. Many of you have met Bob.
Okay. For the fourth quarter, you saw total revenue increase 7% to $1.2 billion, management solutions revenue was up 7% to 9 -- a little bit over $900 million, driven by additional product penetration, into our ancillary services, which currently is mostly ERTC and also price realization. We continue to see strong attachment of our HR Solutions, retirement and time and attendance of products.
Demand for our ERTC service remained strong, as John mentioned, and it contributed approximately 1% to 2% to total revenue growth for the full year. Demand for this mid service along with our internal execution have continued to exceed our expectations, while ERTC has been a tailwind and we expect demand to continue into fiscal year '24, it will become a moderate headwind next year, especially in the back half of the year where it will become more of a headwind.
PEO and insurance solutions revenue increased 5% to $300 million, driven by higher revenue per client and growth in average worksite employees. The rate of growth was tempered a bit by lower medical plan sales and participant borrowings, along with continued preference for ASO in this environment. We expect these trends will start to normalize as we progress through fiscal 2024 that won't be evident necessarily in Q1, and I'll talk about that in a little bit.
Interest on funds held for clients increased 69% to $25 million primarily due to higher average interest rates, partially offset by realized losses taken in Q4 as we reposition the portfolio heading into the back half of this year. Total expenses increased 3% to $776 million since growth was largely attributable to higher headcount, wage rates in general costs to support growth in the business. Operating income increased 15% to $453 million with an operating margin of just under 37%, a 240 basis point expansion over the prior year period. Diluted earnings per share increased 18% to $0.97 per share and adjusted diluted earnings per share increased 20% for the quarter, to again $0.97 per share.
Let me quickly summarize our full year results. Total revenue increased 9% to $5 billion and total service revenue increased 8% to $4.9 billion. As you are all aware, we raised guidance a number of times during the year. Management Solutions increased 8% to $3.7 billion, premium on insurance increased 6% to $1.2 billion. Total expenses were up 7% to $3 billion. Operating income increased 10% with a margin of 40.6%. John mentioned this earlier, that's a 70 basis point expansion over the prior year. The leverage in the model was pretty evident.
Other income net increased by over $30 million due to higher average interest rates and average invested balances within the corporate investment portfolio. Diluted earnings per share increased 12% to $4.30 per share and adjusted diluted earnings per share increased 13% to $4.27 per share. Our financial position remains rock-solid with cash, restricted cash and total corporate investments more than $1.6 billion and total borrowings of approximately $808 million as of May 2023.
Cash flow from operations was $1.7 billion for the fiscal year, an increase of 13% from the prior year, driven by higher net income and changes in working capital. Free cash flow generated for the year was $1.5 billion, up 15% year-over-Year. And while it's easy to gloss over those numbers, I think it is really important that when we report numbers, the quality of our earnings and the our quality of our cash is very-very strong as noted by some of you, not only do we deliver on the topline, but we deliver it in a quality way on the bottom line and we intend to continue to do that. We paid out a total of $1.2 billion in dividends during fiscal 2023, or 70% of our net income on a 12-month rolling return-on-equity with the stellar 48% with an arrow pointing up.
Now, let me turn to guidance for the upcoming fiscal year ending May 2024. Our current outlook, as you saw, is as follows. Management solutions expected to grow in the range of 5% to 6%. PEO and insurance solutions expected to grow in the range of 6% to 9%, widen that a bit just to accommodate the fact that sometimes attachment on insurance can vary from quarter-to-quarter and from year-to-year as we saw last year.
Interest on funds held for clients is expected to be in the range of about $135 million to $145 million. Total revenue is expected to grow in the range of 6% to 7%. Operating income margin is expected to be in the range of 41% to 42%. Other income net is expected to be income in the range of $30 million to $35 million. And then, our effective income tax rate is expected to be in the range of 24% to 25%. Adjusted diluted earnings per share expected to grow in the range of 9% to 10%.
This outlook assume current macro economic environment, which as you know has some uncertainty surrounding future interest rate changes in the economy. We have better visibility in the first half of fiscal 2024. As each quarter progresses, we will have a little better visibility into the remaining quarters in the year.
For the first half of fiscal 2024 and the first quarter, we expect total revenue growth to be approximately 6%. That's the first half and the first quarter. We anticipate operating margins for the first quarter to be approximately 41%, or due to a little bit on your modeling. And we expect PEO and insurance solutions revenue to be below the low-end of the range for the first quarter, then it will be solidly in the range. That's our expectation at this point.
Before you ask me the question, I will answer the first quarter was actually the strongest quarter of the year on PEO last year and as a consequence, the compare will be a little bit tougher and we expect the business build as we go through the year. Of course, all of this is subject to our current assumptions and they can change. We'll update you again on the first quarter call. There's a number of questions because it's, of course, the time when we give annual guidance, so if I could just ask for your forbearance on something, which is to say, ask a question and limit yourself to one follow now, I will say I understand some of those questions will be compound questions, but if it's a five-part compound question that violates the rule. So, but just so we can get through the call without going excessively long.
With all of that, we'll refer you to our investor slides on our website for additional information. And I'll turn the call back over to John.