UBS lowered its rating of Charles Schwab stock to sell from neutral on Wednesday, saying the financial services company is facing barriers to growth and revenue that put the bull case for the stock "on shaky ground."

"The company has a strong customer franchise, but is facing headwinds to [balance sheet] growth from yield sensitive customers, an increasing regulatory burden, and limited rate upside," UBS analyst Brennan Hawken wrote in a note to investors. "We see revenue headwinds at the same time as risk to upward pressure on expenses."

UBS lowered its estimates for Charles Schwab's full year 2019 earnings to $2.65 a share.

"As a result, we think expectations may be too high and could put the stock at risk, particularly given we do not see buybacks as enough to cushion the blow to the growth story," Hawken added.

Charles Schwab shares closed down 1.3 percent in at $46.45 a share.

UBS also lowered its price target on Charles Schwab to $42 a share from $48.