• Americans tend to overspend during the holiday shopping season, and this year will be no different, according to forecasts.
• Millennials, many of whom are now parents of school-age children, are leading the charge, a new survey says.
• However, leaning on credit cards or buy now, pay later plans to purchase gifts will come at a high cost if those balances aren't paid off quickly.

Parents tend to splurge on their children during the holidays.

This year, 63% of millennials, many of whom now have school-age children of their own, said they plan to spend the same or more on holiday shopping as they did last year — the highest share of any generation, according to a quarterly report by TransUnion.

Millennials are also more likely to say their income went up over the last few months and that they expect their earnings potential to increase again in the year ahead. TransUnion polled 3,000 adults in October.

"I see a lot of optimism going into the holiday season," said Charlie Wise, TransUnion's senior vice president and head of global research and consulting.

For many in this group, recent wage gains have outpaced rising prices and, although the broader unemployment rate has ticked higher, "we are still seeing a steady employment situation," Wise said. "When people have jobs, that confidence is going to translate into spending."

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"It's clear that millennials will play the largest role this holiday shopping season with the greatest expected spend," Wise said.

Holiday spending between Nov. 1 and Dec. 31 is forecast to increase to a record total of $979.5 billion to $989 billion, according to the National Retail Federation.

Even as credit card debt tops $1.17 trillion, holiday shoppers expect to spend, on average, $1,778, up 8% compared with last year, Deloitte's holiday retail survey found.

Meanwhile, 28% of holiday shoppers surveyed in September said they still had not paid off the gifts they purchased for their loved ones last year, according to a holiday spending report by NerdWallet, which polled more than 1,700 adults.  

Holiday spending may lead to holiday debt

While most shoppers — 74% — use credit cards to buy holiday gifts, 28% will dip into savings to make their purchases, and 16% will lean on buy now, pay later services, NerdWallet found. Survey respondents could choose multiple payment methods.

Buy now, pay later is one of the fastest-growing categories in consumer finance and is expected to become more popular in the weeks ahead, according to the most recent data from Adobe. Adobe forecasts buy now, pay later spending will peak on Cyber Monday with a new single-day record of $993 million.

However, managing multiple buy now, pay later loans with different payment dates may make it more likely for consumers to get in over their heads, some experts have cautioned — even more than with credit cards, which are simpler to account for, despite sky-high interest rates.

Sometimes, the option to pay in installments can make financial sense, especially at 0% interest, according to Marshall Lux, a senior fellow at the Mossavar-Rahmani Center for Business and Government at the Harvard Kennedy School.

"If used properly, it's great," Lux said.

"But a lot of people are going to spread out purchases over a longer period of time and then you get into high interest and a cycle of debt," he said.

The more buy now, pay later accounts consumers have open at once, the more prone they become to overspending, missed or late payments and poor credit history, other research shows.

If a consumer misses a payment, there could be late fees, deferred interest or other penalties, depending on the lender. In some cases, those interest rates can be as high as 30%, rivaling the highest credit card charges. 

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