Before you book
The rule that stops more runners than anything else at the border
Every Vietnam e-visa approval letter names one entry port. That is the only place you are allowed to enter the country. Officers at Moc Bai check the letter against the gate you are standing at, and if the two do not match, you do not get in.
It sounds too simple to be the number one refusal cause, and that is exactly why it is. Most runners turned back at Moc Bai did not have a passport problem, an overstay problem, or a visa problem. They had a port problem: the e-visa said Tan Son Nhat, or Noi Bai, or left the port unclear, and the border would not bend the rule.
There is no fix-it window at the border. The officer cannot edit an e-visa and will not write a note. You either enter through the port on the letter, or you do not enter Vietnam through Moc Bai that day. For a Da Lat runner that means a 300 km drive down QL20, a border crossing, and a 300 km drive back, all for nothing. The four windows of that crossing are laid out on the Moc Bai crossing guide.
The good news is the check takes thirty seconds, and it should happen the night before the run, not at the window. This page shows where to look on your approval letter, what the port should say, and what to do if it says something else.
The 30-second check
Find the port on your approval letter tonight, not at the window
Your e-visa arrives as a PDF approval letter from the government portal. The letter has a table near the top: full name, date of birth, nationality, passport number, visa type, validity dates, and one line for the entry port. That line decides whether Moc Bai lets you in.
The entry port is printed in English, usually with the Vietnamese name beside it. For the Da Lat run it should read Moc Bai International Border Gate, with Bo Moc Bai, the Vietnamese name for the gate, next to it. Either form of the Moc Bai name is the right answer. Anything else is the wrong answer.
Three more fields to compare while the letter is open, because the port is not the only thing that gets runners refused:
Passport number. One wrong digit is enough. Compare it digit by digit against the passport you will carry, not the passport you used last year.
Nationality. It must match the passport exactly. A visa issued to a different passport will not transfer.
Validity dates. The letter shows when the visa starts and when it ends. If the run happens before the start date, the visa is not active yet, and the officer treats it as no visa at all.
The whole check takes about a minute. Print the letter after you have checked it, because Moc Bai wants paper: the QR code on the letter gets scanned at the desk, and a phone screen is a gamble most officers will not take. Two printed copies is the safe habit, one in your bag and one in your pocket.
What goes wrong
The wrong answers we see on Da Lat runners' letters
The e-visa application form asks you to pick the entry port from a drop-down list, and the list is long: airports and land gates across the whole country. People pick the wrong line for understandable reasons, and the mistake only surfaces at the border. The usual ones:
Tan Son Nhat airport
The most common wrong answer by far. The logic is clear: the sleeper bus from Da Lat arrives in Ho Chi Minh City, and Tan Son Nhat is the airport there. But you are not flying anywhere. The run crosses the land border at Moc Bai, and the e-visa must say Moc Bai, not the airport that happens to sit near the bus station.
Noi Bai, Da Nang, Cam Ranh
Any airport port has the same problem. If the letter names an airport, the only gate that will accept it is that airport's immigration desk.
Xa Mat or another Cambodia land gate
Xa Mat is also in Tay Ninh province, which makes the mix-up feel close, but it is a different crossing about 90 kilometers north of Moc Bai, and it is not where the Da Lat run goes.
A blank or unclear port line
Some letters arrive without a clear port entry. A letter with no matching port is a refusal waiting to happen, because the officer has nothing to check against.
Lao Bao
This one comes from mixing up the network's other border. Lao Bao is the Vietnam-Laos crossing used by the Da Nang and Hoi An desks, not the Cambodia run from Da Lat. The Da Lat run is Moc Bai, full stop. If your letter says Lao Bao, you are holding the wrong visa for this trip.
The pattern is simple: the port on the letter must be the exact gate you cross. Not the nearest airport, not the next town over, not a gate in the same province.
The fix
Wrong port on the letter: what actually happens next
Here is the uncomfortable truth: nothing at the border can fix a wrong entry port. No officer at Moc Bai can edit the letter, stamp a correction, or wave you through on the strength of your story. The e-visa is tied to the port you applied for, and that decision was made when you submitted the form. By the time you are standing at the window, it is too late for this visa.
That leaves two real paths.
Reapply with the right port. The government portal processes a fresh e-visa application for the correct entry gate. You pay the application fee again, and processing takes its usual time, so this only works if your buffer allows it. If your Da Lat run has a hard date and the reapplication will not land in time, do not book the run expecting the visa to catch up. Sort the visa first, then book.
Cross through the port on your letter. If the letter says Tan Son Nhat, that is the only place the visa works. Flying into Tan Son Nhat and running from the Ho Chi Minh City side is a real option for some travelers, and the HCMC visa run desk runs the same Moc Bai crossing from the other end. It costs more than a Da Lat run, but it salvages a visa that would otherwise be wasted.
What never works: showing up at Moc Bai with the wrong letter and hoping. The refusal is logged, and a refused entry at a land border is a small flag on your record that makes the next application slower to approve. It is not a ban, but it is a headache you do not need.
The fixer on a Da Lat run cannot help with a wrong port either. The fixer handles the Cambodia visa, the forms, and the queues, as the Cambodia visa page explains. He cannot rewrite a Vietnamese e-visa. That is why the desk reviews your documents before departure, and why the e-visa add-on is filed with Moc Bai already selected.
The easy version
When the visa desk files it, Moc Bai is already on the form
Most Da Lat runners are not applying for an e-visa from scratch. They are already in Vietnam on a visa that is running out, and the run to Moc Bai is how they reset their stay. For that group the move is the 90-day e-visa add-on: the visa desk files a fresh e-visa while you are on the road, and you re-enter Moc Bai with a new 90-day stay. The full walkthrough of that service is on the 90-day e-visa guide.
The add-on exists because of a timing rule. Vietnam only lets you apply for a new visa after you have left the country, which is why you cannot just extend from Da Lat. The run solves it: the car gets you to Moc Bai, Vietnam stamps you out, and the moment that exit stamp is photographed and sent to the desk, the application goes in. By the time you have crossed into Cambodia and turned around, the new e-visa is processing, and once it clears, the desk messages you the green light to walk back through.
Three things the desk handles that self-applicants get wrong:
The entry port. Every add-on application is filed with Moc Bai pre-selected. The desk has filed hundreds of these through this exact gate, so the port line is never a surprise at the window.
The documents. Passport page, portrait, and the Vietnam address fields go through a review before departure, not after. Bad photos and mismatched passport numbers get caught in Da Lat, where they can be fixed, instead of at Moc Bai, where they cannot.
The timing. Processing tiers run from standard to rush, and the desk tracks the government portal so you are not refreshing it yourself from a border bench. Rush tiers need a weekday exit, because immigration processes e-visas Monday to Friday.
The tiers and prices sit on the prices page under the e-visa section, and the cost guide shows how the add-on fits into the full day's total.
Quick answers
E-visa entry port questions, short answers
Can I enter Vietnam at Moc Bai with an e-visa?
Yes. Moc Bai International Border Gate is on the official e-visa entry list, and it is the gate the Da Lat visa run uses. The e-visa must show Moc Bai as the entry port, or the gate will not accept it.
What happens if my e-visa says a different entry port?
You will be refused at Moc Bai. The e-visa is only valid at the port printed on the approval letter, officers cannot change it, and a refusal gets logged against your passport.
How do I check the entry port on my e-visa?
Open the approval PDF and read the entry port line in the personal details table. It should say Moc Bai International Border Gate. Compare the passport number and validity dates on the same line while you are there.
Can the border officer fix a wrong entry port?
No. There is no correction window at Moc Bai. You either reapply with the correct port or enter through the port named on your letter.
Does my exit port have to match my entry port?
No. The entry port on the e-visa is fixed, but you can exit through any approved border gate. On a Da Lat run you exit Moc Bai, cross to Cambodia, and re-enter Moc Bai, because the run is built around that same gate.
When is the e-visa add-on filed on a run?
Right after Vietnam stamps you out at Moc Bai. Immigration only accepts the application once you have left the country, and the desk files it with Moc Bai pre-selected as the entry port.
Night-before checklist
Five checks before the car leaves Da Lat
- Entry port says Moc Bai International Border Gate
- Passport number matches, digit by digit
- Nationality matches the passport you carry
- Run date sits inside the visa validity window
- Two printed copies of the approval letter packed
Skip the port lottery
Add the 90-day e-visa to your booking and the desk files it with Moc Bai pre-selected, documents reviewed before the car leaves. You carry your passport; the desk carries the paperwork.
Same border, other cities
Running Moc Bai from somewhere else?
The e-visa port rule applies at every gate in the country, so whichever desk you run with, the letter has to name your border. From Ho Chi Minh City, the HCMC desk reaches Bavet in about two hours. Up the coast, Nha Trang visa runs use the same corridor, and the visarun.vn hub compares every crossing if you are planning a longer trip.
More Da Lat reading: the Moc Bai crossing guide walks through the four windows in order, the Cambodia visa page covers the one counter that decides the outbound leg, and the step-by-step guide runs the whole day from Da Lat pickup to evening drop-off.