The single biggest gap in UK side-hustle calculators is the multi-platform case. Most calcs ask “what tax do I owe on my Etsy profit” or “what tax on my YouTube ad revenue” — but real side hustlers usually have several platforms running at once. Etsy plus Vinted. YouTube plus DistroKid plus Patreon. Reseller across eBay, Vinted and Depop simultaneously.
The platforms each report to HMRC independently, but HMRC’s tax framework treats them as one self-employment activity. So the single most common confusion is:
“Each of my platforms is under £1,700 — am I in the clear?”
No, because the £1,700 is a reporting threshold, per-platform. The tax threshold is the £1,000 trading allowance, applied to combined trading income. £600 on Etsy + £600 on Vinted + £600 on Depop = £1,800 total, £800 over the allowance, fully taxable. None of the platforms reports — but Self Assessment is still required.
This calculator does the combined-income maths. Enter PAYE income (if any), then per-platform profit numbers. The output shows:
- Combined side-hustle profit
- Whether you need Self Assessment
- Income tax owed via Self Assessment (with marginal stacking on top of PAYE)
- Class 4 NI on combined self-employment profit
- Total HMRC bill
- Combined take-home from all your side platforms
- Per-platform contribution to the tax bill (which platform is driving your liability)
Why per-platform contribution helps
Side-hustle decisions are usually allocation decisions. “Should I spend more time on YouTube or on Etsy?” The tax cost matters: if Etsy revenue costs you 20% basic-rate tax and your YouTube income is in the 40% band, your effective hourly return per pound earned differs across platforms.
The attribution shown isn’t a precise marginal rate — that would require knowing which platform’s income happened “first” in the band stack, which is artificial. It’s a proportional split: each platform takes a share of the total bill equal to its share of total side profit. Useful enough for comparison, simple enough to interpret.
Reporting vs tax — different time periods, different thresholds
Two systems run in parallel:
| Reporting (per platform) | Tax (combined) | |
|---|---|---|
| Threshold | £1,700 OR 30 items | £1,000 trading allowance |
| Time period | Calendar year (1 Jan – 31 Dec) | Tax year (6 Apr – 5 Apr) |
| Counts | Per platform separately | All platforms combined |
| What happens | Platform shares your details with HMRC | You owe Self Assessment |
Don’t conflate the two. A platform might report you while you owe no tax (e.g., personal-items-at-a-loss reseller on Vinted). You might owe tax with no platform reporting you (e.g., £600 across each of three platforms, none individually reaching £1,700). The two questions answer separately.
For the per-platform reporting question: see the HMRC platform reporting checker, one platform at a time.
For the combined tax question: the calculator above.
Per-platform PROFIT, not gross
Each input asks for profit — sale revenue minus fees minus direct costs. Most users will need to compute profit for each platform separately first:
- Etsy → use the Etsy fee calculator to get profit per sale; aggregate across the year
- Vinted → use the Vinted profit calculator
- Depop → use the Depop fee calculator
- Streaming → currently you’d track DistroKid statements directly; calc coming
- YouTube/TikTok → use AdSense / TikTok payouts, less any agency fees and direct costs (equipment depreciation, software subscriptions)
Then enter each platform’s annual profit total in the calculator above. The tax engine doesn’t care whether you sold 200 items on Etsy or one job-lot on eBay — only the profit total per source matters at the tax-calc stage.