How would you handle a salesperson who meets/achieve their monthly target but is consistently late every single day?

You can insist in the form of a request. My policy is Organization require business not the punctuality provided it will not affect the morale of others in the Sales Team.  Out door sales persons jobs are time adjusted to their list of customers. Let them contribute, we can accept and adjust as it is to become part of our general policy on exceptional circumstances.

The main goal of his work is achieved. It's reasonable to find out about the reason and discuss that issue.

Although punctuality is so important in any organization, however when working in sales, the targets achieved should matter more than anything else.

Sales people being late should not bother one if they are able to achieve their targets. However, he should be coaxed to come on time.

Being punctual strengthens and reveals your integrity. If you tell someone that you will meet them at a certain time, you have essentially made them a promise. And if you say you’ll be there at8:00, and yet arrive at8:15, you have essentially broken that promise. Being on time shows others that you are a man of your word.

Being punctual shows you are dependable. A man can always be found at his post, carrying out the duties needful for that time. People know they can rely on such a man – if he says he will be there, he’ll be there. But if a man is not punctual, others cannot depend on him — they do not know where he will be when they need him. His associates will begin to feel he cannot organize his own time, and these doubts will seep into matters beyond the clock, as it naturally raises the question: “If he is careless about time, what else is he careless about?”

Benjamin Franklin once said to an employee who was always late, but always ready with an excuse:  “I have generally found that the man who is good at an excuse is good for nothing else.”

Being punctual builds your self-confidence. Showing up on time not only tells other people you are dependable, it teaches you that you can depend on yourself. The more you keep the promises you make, the more your self-confidence will grow. And the more you gain in self-mastery, the less you will be at the mercy of your compulsions and habits, and the more in control of your life you will feel.

Being punctual assures you’re at your best. After riding someone’s bumper, speeding like a maniac, scanning for cops, and cursing at red lights, it’s hard to then turn your focus to making a presentation at a meeting or charming a date – you’re shaky and depleted from the adrenaline and stress. But when you show up on time, better yet a little early, you have a few minutes to collect your thoughts, review your materials, and get your game face on.

“Soldiers should be minutemen. Punctuality is one of the most valuable habits a soldier can possess.” –Christopher Columbus Andrews, Hints to Company Officers on Their Military Duties,1863

Being punctual builds and reveals your discipline. The punctual man shows that he can organize his time, that he pays attention to details, and that he can put aside this to do that– he can set aside a pleasure to take care of business.

“’There is great dignity in being waited for,’ said one who was in this habit, and who had not much of which he need be vain, unless it was this want of promptness.” –John Todd, The Students Manual,1854

Being punctual shows your humility. That bumper sticker maxim: “Always late, but worth the wait” shows that tardiness and an overestimation of one’s worth sometimes go hand in hand. People will be glad to see you when you arrive, but they would have been gladder still had you come on time.

In laymans terms, if my employee can not be punctual then he/she does not respect the job; even if he/she is meeting sales target. 

I do agree if sales person achieves monthly target we can be flexible for the 'time' factor. But, as a manager we can't allow him to continue the same. We can have one to one discussion and explain to him the benefits of punctuality(as nicely explained by Ms. Kathy) that this may affect his promotion and can also motivate him by saying situation will arise that his present colleagues may be reporting to him where in it will be difficult for him to control them. Leader is expected to set an example to others. . 

Should be treated just like any other team members

Whatever the company achieved sales of

BEING ALWAYS LATE THAT ONLY MEAN THAT THE PERSON DON'T RESPECT THE COMPANY RULE AND WHAT EVER SALE IS MAKING SHOULD NOT GIVE HIM ADVANTAGE TO BE FREE WITHOUT LIMIT WE SHOULD TAKE ACTION ABOUT IT TO SHOW FOR THE OTHER TEAM THE EXAMPLE 

I agree with most of the answers to colleagues

Im sure his main job and goal to achieved , so you need to to find out the reason then you have to discuss with him/her the issue and what is going on....

I'm trying to advise him attendance and lack of delay because that would have a material payoff bigger and more incentives either for me is to achieve a sales target which is the most important goal