Delaware and New York are both members of the Drivers License Compact (DLC) and Non-Resident Violator Compact (NRVC). As members of the DLC it means that if you were convicted of the seat belt offense in Delaware that the DE courts would then inform the New York Department of Motor Vehicles of this conviction.

The NYS DMV does not record convictions of moving traffic violations by NYS non-commercial licensed drivers in other jurisdictions, except traffic offenses committed in the provinces of Ontario and Quebec, in Canada. Therefore, except for traffic convictions in Ontario and Quebec, out-of-state traffic convictions are not added to your New York State violation point driving record.

The NRVC requires member states to suspend the license of a driver who gets a traffic ticket for a moving violation, such as your seat belt citation, in another state but fails to pay or otherwise legally comply with the citation.

The NYS DMV discusses this by stating that your New York State license will be suspended if you fail to answer a ticket for a moving violation in any state except Alaska, California, Michigan, Montana, Oregon or Wisconsin (states that are not members of the NRVC).

Furthermore, your license will remain suspended until you answer the ticket. Likewise, drivers from any state, except those from the six states listed above, will have their driver licenses suspended in their own state for failure to answer a moving violation summons in New York State.

So if you fail to pay your ticket in Delaware then you will likely be convicted in DE of the offense when you fail to pay for the ticket or failure to appear in court to contest it. DE may suspend your driving privileges for the unpaid ticket and NYS should suspend your license for not pay this out of state ticket.