Discipline is essential; however, how you implement it is your choice. You have an option to introduce rules as mentioned by Ulalme with degrees of punishment as applicable. Penalties are important; however, they bring their frictions along with them.
You can alternatively take a different approach. Assuming that you are aware of the reason why they are late? In your capacity as an HR and Management, how far can you go to resolve them? Have you found the options on how to ensure they reach on time?
What are the chief reasons that you have observed so far? Do they stay far away, or are they not able to manage time due to an overload of responsibilities?
It's easy to punish; however, before you set the guidelines and the penalties, please ensure that you did your best to support them. You need to gain confidence before you can create frictions.
In case you are not completely aware of the problems faced while reaching the office, consider calling for an All-Hands Meeting or a Focus Group Meeting. Brainstorm with your employees on how to resolve them. Make them a partner in this project to maintain discipline within the firm. Every employee may have their unique problem for not being able to reach the office on time. Please make sure you do enough to support them before you implement penalties. You can take this opportunity and build a Peer-To-Peer Mentoring Program. Let your employees mentor each other through these challenges. What one cannot think, the other may offer as a solution.
Here are a few options for you to consider. The first option for you is to offer pick-up and drop. That way you are least likely to miss out on timeliness.
In case you don't have the budget to fund the transport, can you initiate a ride-sharing process? There are apps such as Let's Ride that allow you to carpool or bike pool.
In case this is not possible, please consider the option to offer flexi-timing, where the employee logs in for 8.5 hours and clocks it within the office time period of 8.00 am - 5.00 pm or 9.00 am - 6.00 pm. That way you will have fewer hassles to penalize. The employees may actually welcome this with more productivity.
In an office I worked in, we had several escalations while managing late reporting to work. Hence the Centre Lead called for a Process Improvement Meeting every day in the first hour. Everyone was free to join and contribute to it, irrespective of their roles and reporting orders; they could pick any project they want. This made the interest level in the employees shoot high and the ownership increase. Everybody wanted to be a part of a Process Improvement Program in some or the other project. Needless to mention, this was a high visibility event. It was a zero-cost employee engagement-building program that worked brilliantly.
In your situation, you may need to think differently. Employee satisfaction doesn't lie in the pay package or the designation but in the work culture that you build.
Engage them meaningfully for growth, towards a shared vision, and it will offer the best payoff ever!
Last but not least, please remember it's always easy to punish, but it takes eons to build trust. May you utilize this opportunity to build a better firm.
Wishing you all the best!