2 jobs tax question

Shrinkydoodle

I have a part time job teaching and earn around £8.5k a year. I've been approached by an online training company to write a course for them and have offered a one off payment of £1500. As both incomes come to under my tax allowance of £12500, does that mean that I will not need to pay any tax, or is it different as they're from 2 different sources? As I'm on PAYE, how do I declare the one off payment with the tax man? 
Also, I've been thinking about selling courses (video) myself through Skillshare, I assume I would have to declare this income too?...

Savvy_Sue

You won't need to pay any tax, but you'd declare it through a tax return. If you're planning to increase your income from self-employment, then it would be well worth registering as self-employed and doing tax returns: you'd declare your employed income (on which you may not have paid any tax anyway), but add your self-employed income (on which you still may not have to pay any tax). 

Shrinkydoodle

Savvy_Sue said:

You won't need to pay any tax, but you'd declare it through a tax return. If you're planning to increase your income from self-employment, then it would be well worth registering as self-employed and doing tax returns: you'd declare your employed income (on which you may not have paid any tax anyway), but add your self-employed income (on which you still may not have to pay any tax). 

That's great. Thank you, Sue.