No service records would make me investigate a used car more closely. They would not, by themselves, make me reject it. A missing record tells you that you do not have proof of a service. It does not establish that the service never happened, and it certainly does not establish that it did.
That distinction is easy to lose while scrolling through a vehicle history report. CARFAX explains that its reports depend on information supplied to it and may not include everything about a vehicle. An empty stretch in the report is a question to pursue, not a mechanical diagnosis.
The kind of report matters as well. NMVTIS focuses on title and related history, including salvage, total-loss and odometer information. Maintenance history is outside that report's purpose. Buying another title report will not necessarily answer whether the previous owner kept up with service.
Find the gap that could change your decision
There is little value in demanding a perfect paper trail simply because a car is used. There is considerable value in finding out whether an expensive service you are counting on has actually been done. Start with the maintenance requirements for the exact model, engine and year. Then work through the records available with a technician who knows that vehicle.
An invoice with a date, mileage, VIN and description of work is more useful than “the previous owner took great care of it.” A dealer's reconditioning invoice is useful too, but it documents the work performed for this sale. An oil change last week does not reconstruct years of ownership.
Where paperwork is available, look at what it actually says. “Vehicle serviced” might be all the detail a history report received. A full invoice may explain much more. Let the selling dealer try to locate supporting records, with previous owners' personal information removed. A useful answer may already exist without anyone needing to speculate.
Imagine two similar cars at the same price. One has a dated invoice for the particular major service your technician says matters. The other has no proof, and that service cannot be established through the available inspection. If buying the second car means budgeting to have the work done, the two asking prices no longer represent the same starting point. That is a reason to revisit the offer, not a reason to declare the second car ruined.
An inspection cannot recreate every missing year
Give the mechanic the missing-history question before the appointment. “Look it over” is less useful than “Here is the service history we have; which important items can you verify, and which remain unknown?” The report should distinguish observed condition, documented work, and work being recommended because its history cannot be established.
Do not expect the technician to certify how the car was treated throughout its life. A sound inspection can help you decide what you are buying today. Some uncertainty will remain, even with a thick folder of receipts. The issue is whether the evidence and the price leave you comfortable taking that uncertainty on.
I would be more concerned about contradictions than an honestly explained gap. A seller claiming every service is documented should be able to show the documents. If the paperwork tells a different story and the explanation keeps changing, there is little reason to rush your decision.
Buy the car on the condition you can establish and the costs you can reasonably plan for. If unresolved maintenance could use money you need for other obligations, keep looking. “Probably fine” is a weak foundation for a purchase that already stretches the budget.