Answer

I could not verify one universal “Siddhi Tap 2026” start date. Siddhi Tap is a Jain austerity done in a specific fasting pattern, and the common vidhi describes it as a monsoon observance with 36 actual fasting days. ( jainsite.com)

Explanation

In one verified 2025/26 Jain community calendar, Paryushan Mahaparva starts on 8 September 2026. Siddhi Tap is often observed in this same monsoon/Paryushan season, so if you mean the general Jain period around Siddhi Tap, that is the nearest dated reference I found. ( oshwalnairobi.org)

Takeaway

So, for 2026, Siddhi Tap does not have one single all-Jain start date; it depends on the local sangh and its calendar. ( jainsite.com)