Although tax cuts and regulatory rollbacks this year fueled small-business optimism to hit its highest level in decades, the latest CNBC|SurveyMonkey Small Business Survey, released Monday, reveals that small-business confidence is starting to cool. After hitting a record high in Q3, the Small Business Confidence index declined from 62 to 59 in the fourth quarter, led by small moves lower in components across the board. This new data from CNBC and SurveyMonkey underscores the idea that while sentiment is at or near record highs, challenges still remain for Main Street. The CNBC/SurveyMonkey Small Business Survey, conducted from Nov. 19–29, polled more than 2,100 small-business owners. The dip in the CNBC/SurveyMonkey Small Business Survey comes at a time when the markets are punctuated by bouts of volatility and economic concerns loom over trade tensions and the shortage of skilled workers. The data supports other small declines in metrics, from the National Federation of Independent Business's monthly read on small-business sentiment in September and October, as well as trends around hiring and labor from Bank of America and Wells Fargo. "Unemployment is down, small businesses are growing, but there are still some very troubling trends," said Todd McCracken, president of the National Small Business Association, in an email to CNBC. "The rate of small-business start-ups and small-business hiring continues to lag, one-quarter of small firms still cannot get the financing they need, and few can afford a good health insurance plan."

Unemployment is down, small businesses are growing, but there are still some very troubling trends. Todd McCracken president, National Small Business Association

He added that "economic security is a huge drive in how small businesses are faring — they're less likely to invest, grow, innovate and so on if they fear economic problems on the horizon." McCracken pointed to polling from the group's membership, which also saw a decline in economic outlook midyear in 2018. For the first time in six quarters, sentiment around business conditions also has taken a slight dip, from 58 percent in Q3 to 55 percent in Q4, although that read is still up 11 percentage points year-over-year, according to the survey.

Positive outlook on tax policy waning

Just 34 percent of small-business owners now say that tax-policy changes will have a positive effect for them in the next 12 months, down from a high of 46 percent kicking off the year, indicating some of the positive sentiment surrounding the law may have waned. Weighing in on the latest results, Laura Wronski, senior research scientist at SurveyMonkey, said, "I would describe it as a slip, not a fall. It's not a huge drop, and still up year-over-year." She added: "Hiring expectations are about the same, but some of the improvements we saw with changes to tax and trade policy were not sustained throughout the course of the year." More small-business owners are questioning the positives the administration's trade policies will have on their bottom lines. Sixteen percent of small-business owners say they expect changes in trade policy will have a positive effect on their businesses in the next 12 months, a new low for the survey. What's more, 1 in 5 business owners surveyed do business with China, and they were nearly twice as likely as others to expect a negative impact on their business. More from CNBC/SurveyMonkey Small Business Survey: Small businesses, desperate to fill open positions, juice job offers

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Skilled-labor shortage still a top concern

On the job market, 18 percent of business owners said they had roles open for at least three months, an increase of 2 percent from Q3 of this year. To help bridge that gap, 56 percent said they were offering higher wages, 31 percent said they were offering to pay for additional training and 27 percent said they were offering additional benefits to workers. Others said they were offering to help pay for student loans and even relaxing policies around things like drug testing and criminal records. "I think it's very interesting that even small-business owners are having to juice their offers a bit because it is a tight hiring market," Wronksi said. "It's great for workers but tough on small-business owners."

Keith Getter | Getty Images

Finding skilled labor has also come up as a top issue in the National Federation of Independent Business' monthly survey, outpacing other major issues, like taxes and government red tape and regulations for more than half of the year in 2018, a trend that could continue into the next year. "Everything is good in this economy, and we will keep moving along, but growth won't be as fast as it could have been if we could fill these job roles," said Bill Dunkelberg, chief economist for the NFIB. And now with midterms complete, Main Street is weighing in on its top priorities for Congress in 2019. Leading the way: spending cuts and deficit reduction (19 percent), followed by immigration (18 percent) and health care (17 percent). Fifteen percent of respondents said they'd like to see increased oversight of the Trump administration, which could very well become a possibility with Democratic control over the House of Representatives. A new Congress could also lead to some uncertainties for Main Street, McCracken said, a potential trend that will head into the new year.

Fifteen percent of CNBC/SurveyMonkey respondents said they'd like to see increased oversight of the Trump administration. Kevin Lamarque | Reuters