Perhaps it's time for Prince Harry to head back to the UK after being in the US for seven months. 

He and his wife, Meghan Markle, along with their son, Archie, purchase a Californian mansion for $14 million in May after leaving a rented mansion in Vancouver Islands, Canada, in March. 

Before purchasing their home, the couple reportedly stayed at producer's Tyler Perry Beverly Hills mansion in March and only moved to their new place in May. 

As of writing, the Duke of Sussex has been in the US for at least 152 days. If it reaches 183 days, the 36-year-old may be legally liable to start paying for his taxes there. 

Top Los Angeles lawyer David Holtz assumed that the Internal Revenue Service is looking at the Brit "very closely."

"This is a big deal," he added. "If Harry's been in the US for 183 days straight, then he's done. But it is safe to assume they have had lawyers and tax experts grinding away on this issue for months."

Prince Harry is facing to pay both US federal and Californian state taxes under the "substantial presence test" that demands any foreigner who stays in the country for 183 days in three years to start paying US taxes on their worldwide earnings.

Not only is the dad-of-one paying a "monumental amount" for his taxes, but this could also open an investigation for the Royal Family, as the IRS wants to know all of the Prince's sources of income. 

It won't just be his Netflix deal or speaking engagements. This includes monetary allowances from Prince Charles, trust funds, savings accounts, or assets in the UK. 

"That includes paying gift tax on any monetary gifts he received from Prince Charles, and he will have to show any other source of income, including trust funds set up after the death of Princess Diana."

"That means the Royal books will be open to scrutiny. The US taxman is far more zealous than his UK counterpart," another accountant said. 

The Duke and Duchess of Sussex will reportedly earn $1 million for each speech; their deal with the streaming giant is worth to be $3 million to $5 million annually.

Prince Harry and Meghan Markle have an estimated net worth of $24 million. 

Another critical factor is the type of visa Prince Harry used to enter the US. Since he is not using a diplomatic visa, he will be liable for the same taxes in the US as everybody else. 

Meanwhile, Meghan Markle's tax-paying duties still haven't changed, as she is still a US taxpayer. 

News of Prince Harry's monumental US taxes comes after a former head army issued a public plea for the Duke of Sussex to go home to the UK.

According to General Richard Dannatt, veterans will lose out because Prince Harry decided to quit royal life and move to the US with Meghan Markle and Archie. 

The General believes that it is a shame that Prince Harry is no longer connected to the arm forces charities, Invictus Games, to help injured or troubled veterans. 

READ MORE: Prince Harry Criticizes UK for Being Racist; Thanks Meghan Markle for Educating Him