I have been asked by a resident Brit to post this - to avoid confusion
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At the end of 2014 when I got my first Dr license, I rang the Embassy and they said they had stopped validating UK licenses and from the Foreign Office website they are still stating just that. Unless things have changed recently Americans we Brits need to get fully tested with provisional license first.
https://www.gov.uk/guidance/living-in-the-dominican-republic
I am not sure you will want to suggest she is incorrect but it may be worth posting the link which clarifies that the UK embassy can no longer validate the legality of ones UK license as presented in Santo Domingo. But they do provide a notorial service as indicated in the link Matilda posted. Big difference.
Driving licenses and driving in the Dominican Republic
A UK or International driving license is valid to drive in the DR for three months. After three months, a Dominican driving license is required. It can be requested to the “Oficina de Tránsito Terrestre”, Ministry of Public Works & Communications. (See contact details below)
Contact details for the OTT
In Santo Domingo:
Ministry of Public Works Ave. Tiradentes with Avenida San Cristobal Tel. 809 565 2811
In Puerto Plata:
Calle Hermanas Mirabal Tel. 809 244 4084
The Embassy cannot certify that your British license is valid.
To clarify the 90 day rule ,mentioned , it only applies to persons legally in the country with a valid visa or residency and not overstayers.