NEW YORK (Reuters) - Visa Inc (V.N: Quote, Profile, Research), the world's largest credit card network, said on Monday that quarterly earnings rose, helped by declining tax expense, but the company's shares fell in after-market trading.

The San Francisco-based company said net income for its fiscal second quarter ended March 31 was $314 million, or 39 cents per class A share, compared with pro forma results of $246 million in the same quarter last year.

Visa went public in March and these results are its first as a public company.

Operating income fell during the quarter, to $349 million from a pro forma $394 million in the same quarter in 2007, hurt by higher advertising and marketing expenses and more money being set aside for litigation.

Operating revenue rose to $1.45 billion from $1.19 billion.

In after-market trading, Visa traded at $72.67, down nearly 4 percent from Monday's close of $75.63.

(Reporting by Dan Wilchins; Editing by Andre Grenon)