Refunds and Cancellation

Seven days, no questions, on a first purchase.

The refund

If your first purchase of a licence disappoints you, write within seven days of payment to v.s.sajesh@gmail.com from the email used at checkout, and the payment is returned in full — no reason needed. Refunds are issued to the original payment method, typically within 5–7 working days of processing.

Cancellation

Cancel any time from the billing page. Renewals stop at once; access continues to the end of the period already paid. Partial periods after the seven-day window are not refunded — the annual plan's discount already prices its commitment.

The free tier is the trial

Part I of the book, the library with its measured residuals, and the sources are free precisely so a purchase is never blind. Read first; pay after.

Last revised 9 August 2026.