Square’s popular free invoicing software is becoming the company’s next big subscription service. The company is poised to announce a paid subscription offering called Invoices Plus, which will offer sellers a set of advanced features, including some that had previously been available with the free service. The service itself had been quietly introduced to individual sellers, but has not yet been publicly announced.

Some sellers who were already using Square Invoices were recently alerted to the upcoming changes via email.

In the announcement shared with some sellers (the details of which can also be viewed here on a Square Seller Community forum), the new subscription will include a series of features that were released in the past year as part of a limited trial.

This includes multi-package estimates, custom invoice templates and custom invoice fields. These will now become a part of Invoices Plus, as will two other features: the ability to automatically convert accepted estimates to invoices and the ability to build milestone-based schedules (three-plus installment invoices). Square’s announcement said it will introduce a “trial” button next to these features in the Square Invoices software to alert customers to the upcoming capabilities (see below).

Square’s free invoicing software will not go away, the announcement noted. Sellers will be able to send unlimited invoices for free, as well as estimates and contracts, with the free plan. Free users will also be able to use invoice tracking, reminders and reporting tools.

The free plan has historically relied on processing fees to generate revenue. At present, this is 2.9% + $0.30 per invoice paid online by check or debit card plus a 1% fee per ACH transaction, per Square’s website. (Fees are slightly lower on in-person transactions and slightly higher for “card on file” transactions.) Pricing for the new, paid subscription has not yet been publicly announced.

A Square employee had explained the reasoning behind the change on the community forum site. They noted that many of Square’s other products — like Square Online, Appointments, Square for Retail and Square for Restaurants — also offer both a free and paid tier. And although Square charges processing fees for Square Invoices, they aren’t enough to fuel its product development. With Invoices Plus, they said, the company aims to compete more directly with paid invoicing apps and products and the more advanced features those products offer.

Reached for comment, Square confirmed to TechCrunch Invoices Plus is a software subscription the company plans to announce shortly. But the company didn’t want to share more details until the news is official.

References to the new subscription have also already made their way to the Square app’s code, where they were spotted by iOS developer Steve Moser. The code indicates users who previously used some of the paid-only features will be able to still use them for the time being. But as the announcement also noted, sellers would not be able to use the paid features for free the next time they’re creating new files with Square Invoices.

The new service arrived shortly after Square announced earnings, where it noted its seller business brought in $1.31 billion in revenue (out of the total of $4.68 billion) and $585 million of gross profit in the second quarter, driven in part by continued strong online growth. The company also announced its plan to acquire the buy now, pay later giant Afterpay in a $29 billion deal, speaking to its interest in chasing the broader payments market. The deal also offers Square a way to connect its different products by allowing Afterpay customers to pay their monthly installments through Square’s Cash App, the company said.

An integration between Square and Afterpay is something that could be seen further down the road, as well, one could imagine. That’s something Square also hinted toward in a response to another seller on its community forum site, where a rep updated an older answer to share news of the acquisition, adding Square didn’t “have integration timelines to share at the moment.”