When to mow the lawn after a treatment depends on the treatment applied and a little on the weather.

A lawn needs to be mown at regular intervals, especially during the growing season. This can mean fitting a mowing schedule in around treatments can be difficult. To get the best result from your treatment always follow advice given with the treatment.
After a fertilisation treatment, you shouldn’t mow for three to four days. The majority of fertilisers are granular and need a few days to start to break down. Mowing soon after a treatment risks collecting the fertiliser with the lawn clippings. This would be a waste of the treatment, and would reduce effectiveness.
After a herbicide treatment, you should allow time for the chemical to work into the weed before mowing. This is also a few days.
This time to mow can be sooner if there has been a large amount of rainfall. Fertiliser begins to breaks down in water and the granules will make their way into the ground with rain. If you can still see the fertiliser resting on the grass, then don’t mow.
When to mow the lawn after a treatment
If the lawn contains weeds, the weed control chemical applied needs time to work into the plant. Mowing risks cutting off these leaves, reducing the effectiveness of the weed killer spray. For a complete control of weeds, four days until mowing is ideal.
For fungicide treatments, you should not mow for at least four days afterwards. This is to allow the chemical time to get to work its way into the grass.
If you have an aeration treatment then you do not have to adjust your routine at all. The lawn can be mow the same day in necessary.
The opposite is true for scarification. You may have to wait many weeks before you can mow. With overseeding this may be many months!
The best way to be sure is to read the information which is provided with your treatment. Or just ask The Lawn Man on the day.