Pakistan has confirmed that it is charging an $830 fee to undocumented refugees who want to leave the country.
The exit fee applies to people who arrived without a visa.
In October Pakistan announced that it would deport 1.7 million undocumented foreigners from the country if they did not leave by 1 November.
Most are Afghans, including hundreds of thousands of people who fled Afghanistan when the Taliban retook power in 2021.
Those who have expired visas will be charged depending on how long they have overstayed.
An exit fee does not apply to anyone travelling back to Afghanistan.
Many Afghans who arrived in Pakistan when Kabul fell to the Taliban have faced delays getting documentation, according to groups like Amnesty International.
Pakistan is not a party to the Refugee Convention and has said it does not recognise any of the Afghans living in its borders as refugees.
A senior diplomat in Pakistan told the BBC that the fee was particularly worrying when it was being applied to people who were being relocated on humanitarian grounds.
"In many countries, if you overstay your visa you have to pay or you get booted out," they said.
"The problem is charging those we are taking on humanitarian visas. Not necessarily the people we are taking because they worked for us, but who UNHCR sees as having a humanitarian need. It sets a very bad precedent."
The diplomat said that there had been some early indication that the government could be reviewing the policy, which they said they're encouraging.
The Pakistan authorities did not discuss the possibility of a review with the BBC.
The UNHCR told the BBC it is trying to "resolve the issue".
"We are advocating for the authorities to exempt refugees from these requirements.
"The Government and people of Pakistan have a commendable, decades-long history of providing asylum and protection to Afghan refugees, this needs to continue."
A spokesperson for the country's Ministry of Foreign Affairs said "Pakistani laws, like the immigration laws in other countries including the United Kingdom, have fines and punishments for individuals who overstay their visas or are in violation of immigration laws.
"Any fines that Pakistan has imposed or will impose are in conformity with our laws." (BBC)