Afghan refugees, distinct languages and transgendered citizens are now included in the survey. Around 200,000 members of the armed forces are helping to conduct it.
In 1998, Pakistan conducted its last national population census. Nineteen years later, the nation has begun a new one.
Here are 12 things to know about the census:
1. Since the last one was carried out, the nation's population has exploded
Pakistan's population has exploded since its first census in 1951, four years after the partition of India. At that time, the country had around 34 million inhabitants.
Officials still use the figure of 134.7 million from the last census. But the World Bank estimated the country's population at 190 million in 2015. The nation is believed to be the sixth most populous country in the world.
The census results might cause political boundaries, parliamentary seat allocations and federal funding to shift.
They'll also reveal urbanisation trends, migration, the gender balance, employment levels and educational attainment.
2. Only nine languages are listed
Language is considered an essential tool in evaluating the makeup of multi-ethnic Pakistan — but only nine of the country's estimated 70 will be listed, to the dismay of many communities.
No regional languages from sparsely populated Gilgit-Baltistan will be included, nor will Gujrati, which is spoken by some Muslim immigrants from India. Some believe the lack of recognition will drive their mother-tongue towards oblivion.
3. Faith matters
The census will provide an insight into the true number of religious minorities, especially Christians and Hindus. Estimates are approximate and disputed, ranging from 2 to 10 million for the former and 2.5 to 4.5 million for the latter.
Citizens can declare themselves Muslim, Christian, Hindu or Ahmadi — a community considered non-Muslims by the state.
Otherwise, they can elect to be recognised as "members of scheduled castes" — members of marginalised Hindu families, or "other." There are no separate options for Sikhs, Parsis or Baha'i.
4. Afghan refugees are now included in the census
Officials say that around three million registered and unregistered Afghan refugees in Pakistan will also be counted in the census.
The decision has outraged leaders, particularly in southwestern Balochistan province where the ethnic Baloch population fears it would turn them into a minority in their native region.
Parties in southern Sindh province, particularly in its capital, Karachi, have also opposed the inclusion of Afghans and have demanded the census be postponed until all the refugees return to their country.
But government officials have dismissed those concerns as unfounded and politically-motivated.
5. Transgendered citizens will be counted for the first time
In 2011, Pakistan had taken the decision to allow people who do not consider themselves to be either male or female to have their own gender category on official documents.
Transgendered people will be counted separately for the first time, as enumerators have been informed that those surveyed will have three numeric choices for their gender: 1 for men, 2 for women and 3 for those who declare themselves transgender.
6. The census lasts for 70 days
The process will take approximately 70 days. It will be concluded in two phases. The first one will take place from March 15 to April 15, while the second will be from April 25 to May 25.
Final results are expected by the end of July.
Those who are found guilty of willfully giving false information face a six-month jail term and a financial penalty of around 500 dollars.
7. Why did it take so long to carry out?
As required by the country's constitution, the Pakistani government has to conduct a census every ten years.
Pakistani authorities say the census has not been held due to security concerns. But critics say the actual reason was a lack of political will to undertake an exercise that could unveil the truth about a major population increase and movement of people.
Mansoor Raza, a journalist based in Pakistan who writes for Dawn, told TRT World that censuses always remain a political issue in Pakistan because of the resource distribution arrangements under the National Finance Commission (NFC) awards. NFC is based on demographic imperatives between provinces.
"Any major shifts in demographic contribution will affect not only NFC awards, also the federal job quotas and the configuration of seats in National Assembly," Raza said.
8. Why is the survey taking place now?
"Every government is wary of tinkering with power structures and sets up in Pakistan and the present government is no exception to that. But this time on the intervention of Supreme Court, the Federal Government is forced to swallow the pill of census." Raza said.
The census is coming one year before national parliamentary elections.
"There is a certain level of pressure for making elections more and more transparent and that cannot be accomplished without knowing who lives where," Raza added.
9. Hasty preparations are underway
The Pakistan Bureau of Statistics (PBS) has been primed and ready on the starting blocks for years, but the government only gave its green light less than three months ago.
Opponents say three months is a short period of time to train staff and reassure parties and communities.
"There was very limited time to get everybody on board and ensure everyone feels the importance of being counted," said Hassan Mohtashami, Technical Advisor at the United Nations Population Fund (UNFPA).
10. How will it affect politics?
Besides the exact headcount for better planning, the decennial census affects the nation's balance of power.
"The count actually determines the political power of various ethnicities," said Muddassir Rizvi, head of programmes at the Free and Fair Elections Network.
The population census is also used to assign electoral seats in Pakistan's parliament.
Critics say mainstream and regional political parties have influenced previous census exercises in the country, leading to over-representations of some regions in the parliament.
"The seats in the National Assembly are allocated to each Province/FATA and Federal Territory on the basis of the population in accordance with the last preceding census officially published under Article-51(3) of the Constitution." says Pakistan Bureau of Statistics.
The country's electoral constituencies are also demarcated according to data obtained from census.
11. The military is heavily involved
The census originally was scheduled for March 2016. But it was postponed due to unavailability of army personnel to oversee security.
"Conducting a census is a multi-dimensional and multi-stage exercise which requires planning and coordination across the country in order to reach every household," a PBS spokesperson had said to the country's highest court in July 2016.
Pakistani army announced that it would dispatch 200,000 troops for the exercise. Around 44,000 of the troops will participate directly in the census-taking and making a parallel court, it said.
Army spokesman Major-General Asif Ghafoor said that the institution has been tasked to provide security and ensure the census is conducted in a "smooth" manner.
"A soldier will accompany every civil enumerator and will also collect his own data during the door-to-door campaign. We have put in place a system to immediately verify the information," Ghafoor said.
The PBS's chief statistician, Asif Bajwa, said the army would act as "observers" to ensure enumerators did not inflate local counting.
"Being a local person, the enumerator is susceptible to pressures, because everybody knows that a larger population translates into more jobs, more seats, and more money for the province," Bajwa said.
But that has created some disquiet for the UN who are concerned about the army's role as parallel data collectors.
"The administration of any kind of other questionnaire during the census is (infringing) on the principle of confidentiality," said Mohtashami.
12. How are foreigners counted?
The census gives two options for nationality: Pakistani or foreign.
But the army, which will conduct a parallel count, plans to be more precise mainly because of the country's Afghan refugees who are frequently accused of everything from terrorism to trafficking.
Many local officials fear Afghans could be counted as local and skew demography in favour of ethnic Pashtuns, whose political parties would benefit as a result.
On the other hand, the estimated six million Pakistanis working abroad will not be counted. No information will be collected on internal migration -- necessary to assess the political weight of a province where many people have moved for economic reasons.
This information will be the subject of a separate subsequent survey based on a large sample of the population, according to authorities.