The variations can be wide: In New Zealand, which kept its no.3 ranking this year, it can take one procedure, half a day and little in the way of fees to start a business, but in Suriname and Venezuela, entrepreneurs wait 208 and 144 days respectively, the report noted.
Among the reasons why Singapore retains its top rank is its early adoption not only of electronic filing for public administration, but also a "trade single window," which eases trade by allowing cross-border traders to submit customs data through a single gateway.
(Read more: One-third of global firms planning acquisitions: EY)
"Trading across borders has been easiest in Singapore since 2007," it said, while second-ranked Hong Kong is the easiest place to get construction permits.
But China lags behind Zambia and Rwanda
China edged up to rank at 96 from 99 in 2013 after making it easier for businesses to get credit and enforce contracts, the report said, while the U.S. retained its no.4 ranking.
Ukraine, Rwanda, Russia, the Philippines and Kosovo are among countries improving the most in the past year, the report noted. Ukraine improved the most, rising to rank at 112, from last year's 140, with reforms in eight of the ten topics the data tracks, it said.
Rwanda climbed to rank at 32 from last year's 54, while the Philippines rose to 108 from 133 and Kosovo advanced to 86 from 96.
(Read more: This Worries Us Most About China, Says World Bank)
Myanmar made its debut on the list, ranking at 182 out of a total 189 countries. "Old laws and regulations still apply in Myanmar, including the Companies Act of 1914, the Code of Civil Procedure of 1908 and the Evidence Act, 1872," the report noted. Myanmar requires more than $58,000 in deposit capital before registering a business, it noted.
South Sudan and Libya were also added to the rankings for the first time, coming in at 186 and 187 respectively.
"In Libya the civil code and the civil and commercial procedure codes all date back to 1953. In South Sudan the challenge is not updating old laws and regulations but creating new ones from scratch. This process takes time. Yet since independence in 2011, South Sudan has passed a company law, tax law and insolvency law," it noted.
— By CNBC's Leslie Shaffer. Follow her on Twitter: