The stock market is seeing broad gains this year following a miserable 2022. The technology sector, especially, is outperforming and the Nasdaq-100 index is up 32% year to date. But it still has some ground to make up before reaching its previous all-time high.

Many individual, high-quality technology stocks are doing better in 2023 as well. And yet, share prices of Duolingo (DUOL -1.32%) and Bill.com (BILL -2.86%) remain 23% and 70% below their all-time highs, respectively, despite reporting underlying strength in their businesses. 

Here's why that dichotomy presents a buying opportunity for investors.

1. Duolingo: Transforming language education with AI

Duolingo is the largest digital language education platform in the world with 72.6 million monthly active users. It takes a mobile-first approach that places fun, interactive, and engaging lessons directly into the pocket of its users so they can learn anywhere, anytime. 

The platform operates under a "freemium" revenue model where users can sign up and use base-level features at no cost, with the option to pay a subscription to unlock additional capabilities designed to speed up the learning experience. Duolingo has become the highest-grossing app in the education category in both the Apple App Store and Alphabet's Google Play Store. 

In the first quarter of 2023 (ended March 31), Duolingo had 4.8 million paying subscribers, which represented an all-time high of 8% of its monthly active user base. But that figure could be set to soar thanks to a new subscription tier the company just launched, called Duolingo Max. 

It features two unique tools powered by artificial intelligence (AI); the first is Roleplay, a chatbot that users can converse with to improve their speaking skills. The second is Explain My Answer, which provides personalized feedback to each user based on their mistakes in each lesson. Duolingo has been working on AI since 2013 and it also began collaborating with ChatGPT developer OpenAI in 2021. The new Max features are powered by a combination of in-house AI technology and ChatGPT.

But the company is also using OpenAI's newest GPT-4 technology to craft content for lessons because it's capable of forming structured sentences in multiple languages. This puts more time back in the hands of Duolingo's team to work on more impactful projects. 

Duolingo stock has soared 118% in 2023 so far, but it's still down 23% from its all-time high and that might be a buying opportunity for investors. The company delivered $115.7 million in revenue during Q1, up 43% year over year and well above its prior guidance. The strong result prompted an upward revision to its full-year revenue forecast, to $509 million from $498 million previously. 

As has recently been the case with other companies using AI, the technology could really supercharge Duolingo's financial results going forward. 

2. Bill.com: Solving payment headaches for small businesses

Unlike Duolingo, shares of Bill.com are lagging this year with a 4% loss so far, and they remain 70% below their all-time high price from 2021. Bill.com sacrificed some of its lightning-quick revenue growth to improve its net losses recently, which prompted investors to rethink the company's valuation. Nonetheless, it's a great business and it has an enormous addressable market in front of it. 

Its main platform helps small to medium-sized businesses manage their accounts payable workflows. It features a cloud-based digital inbox where the operator can store all of their incoming invoices, pay them with one click, and sync the transactions with their bookkeeping software. It's designed to eliminate messy paper trails and the headaches that come with missed payments. 

Through an acquisition of Invoice2go in 2021, Bill.com now also manages the accounts receivable side of the equation. Businesses can generate invoices, bill customers, and track incoming payments to ensure the cash keeps flowing. And through a separate acquisition of Divvy in the same year, Bill.com now also offers a budgeting and expense management platform. 

Bill.com has relationships with over 6,000 accounting firms that push its platforms onto their clients. It's a win-win for all parties -- the software makes the accountant's job more efficient, which reduces the time they spend managing each client, which in turn reduces accounting fees for the end-user (the business). As of the recent fiscal 2023 third quarter (ended March 31), Bill.com had 455,300 business customers overall. 

It generated $272.6 million in revenue in the quarter, an increase of 63% year over year. While that's a robust growth rate, it was much slower than the 179% increase it delivered at the same time last year. But on the other hand, the company managed to shrink its GAAP net loss by 64% to $31 million, which is what investors wanted to see in this tough economic environment where reducing risk is key. 

Bill.com generates the majority of its revenue when businesses use its platform to process payments. It's a substantial global opportunity that the company estimates is worth $125 trillion, so it has barely scratched the surface thus far. Plus, it believes there are more than 70 million small to medium-sized businesses that could use its platforms worldwide, placing its current market penetration at just 0.6%. 

Despite Bill.com focusing less on growth and more on inching toward profitability, it still has a significant market to expand into -- it will just capture it a little more slowly. That's a great long-term opportunity for investors who can buy Bill.com stock now at a 70% discount to its all-time high.