Sept 13 (Reuters) - Intuit Inc (INTU.O), known for its small-business accounting and DIY tax-filing software, said on Monday it will acquire email marketing company Mailchimp for about $12 billion in a cash-and-stock deal. The deal, expected to close by the second quarter of fiscal 2022, is Intuit"s biggest-ever acquisition. It will be financed through cash on hand and new debt of about $4.5 billion to $5.0 billion, Intuit said. Last year, the company bought personal finance portal Credit Karma for just over $7 billion. The deal for Atlanta-based Mailchimp, which operates a marketing platform for small and mid-market businesses, will help Intuit expand its product base for small businesses. It comes at a time when fintech companies like Intuit are benefiting from a recovery among small businesses from the pandemic-induced slump. The company has projected profit and revenue levels above estimates for fiscal 2022. Founded in 2001, Mailchimp traces its roots to a Web design agency called the Rocket Science Group, which cofounders Ben Chestnut and Dan Kurzius started to focus on big, corporate clients, according to its website. They shut down the agency in 2007 to focus exclusively on Mailchimp, which the duo ran as an email marketing service for small businesses. Mailchimp now has more than 12 million clients, including online video platform Vimeo Inc (VMEO.O) and nonprofit media organization TED. Mountain View, California-based Intuit"s products include TurboTax, a software that helps Americans file income tax returns, and QuickBooks, a cloud-based application that helps small businesses manage payments. Intuit, which was started in 1983 by Scott Cook and Tom Proulx, went public 10 years later and now has more than 10,000 employees across 20 offices in nine locations worldwide. The deal is expected to add to Intuit"s adjusted earnings for full-year fiscal 2022. Bloomberg reported on the deal talks earlier in September. Morgan Stanley served as financial adviser to Intuit, with Latham & Watkins serving as its legal adviser. Qatalyst Partners and King & Spalding LLP advised Mailchimp.