Declaring Royalty payments

At the moment I run an AE business selling things online, but I sell about 80% of my product to the UK and I assume the effective 20% price increase there has put people off buying as, for the last 2 months sales have only 25% of normal. If this continues I’m thinking of closing the business down at the end of the year as it’s no longer viable.

But I also get some royalty payments for the use of my designs. These won’t stop ( I don’t think I could even stop if I wanted to) It’s for work I did some years ago so confusingly, I won’t be working, but still getting paid.

At the moment I’m lumping them in with the rest of my sales ( I’m not even sure I should do this, but it seemed the easiest thing to do!), but how can I declare them after I close the business down?

They come monthly from the US in $, but can be very variable, from about $30 to around $700 but most times in the $150-250 range. Probably about $2-3000 per year.