Your side-income setup
For trading income, HMRC's entry point is based on gross income before claiming expenses.
Likely next step from these inputs
Trading allowance may cover this
Keep records and use the HMRC checker if anything else is going on.
What this means
For a small side-income stream that looks like trading, the first quiet threshold is the £1,000 trading allowance. That does not override other reasons HMRC might still expect a return.