RBS Citizens Financial Group announced Tuesday three major tech upgrades for customers of Citizens Bank and Charter One (a division of RBS Citizens that operates in Illinois, Michigan and Ohio): it replaced its fleet of 1,600 ATMs, implemented a new digital teller system and enhanced its mobile apps.

The new ATMs, which use imaging technology, let customers deposit checks without envelopes. Customers can deposit checks as late as 10 p.m. for funds to post same day. Previously, the cut-off time was 3 p.m.

The news underscores a trend toward imaging-equipped ATMs that's been occurring ever since the passage of the Check 21 Act in 2004, which made it okay to create digital versions of paper checks for processing.

The bank's updated mobile app, meanwhile, now includes PopMoney, a feature that lets customers pay their friends back using an email address, mobile phone number or account details.

"We're making a lot of investments in tech to make life easier for customers," says Brad Conner, vice chairman of consumer banking at RBS Citizens Financial Group.

Customer expectations of banking on their own terms are driving the bank to modernize its tech, says Conner. "We are constantly looking at the art of the possible," he says.

The upgrades are the latest in a series of initiatives designed to improve digital banking. In another recent example, RBS Citizens introduced a $5 overdraft pass, which exempts overdrafts fees on items less than $5.