What this app is
CIS Tax Calculator, published by Youlongtang, is a record-keeping tool. It reads the figures and the rate you type, works the deduction and the VAT lines out of them, and writes an invoice. Carrying on into the app counts as accepting what is written here.
What it is not
Your HMRC registration is not looked up. Which CIS rate applies to you is not decided here, nor is the question of whether the VAT domestic reverse charge covers any particular supply, and nothing at all is filed on your behalf. The guide condenses published HMRC material and links out to gov.uk with the date each entry was last read; the rules move, and a condensed entry is never the full page. The figures you type, the rate you pick, the VAT treatment you accept, and the checking of every deduction against the statement your contractor issues, all remain yours. None of what the app shows is tax or legal advice.
Your data
Invoices and contractor records live on your device only. Keeping a backup of them is your job, as is whatever you do with the invoices once they are sent.
Subscription
CIS Tax Calculator Pro · £39.99 a year · 7 free days for eligible new subscribers
Billing runs through your Apple ID and repeats yearly. Your Apple ID is charged when the purchase is confirmed, or on the day the free week runs out, unless it is switched off at least a day beforehand; after that the same terms carry over into each year. Subscriptions are managed and cancelled under your Apple ID. Writing text invoices and sending them never requires a subscription.
Liability
The app comes as it is. As far as the law permits, Youlongtang carries no liability for loss that follows from relying on a figure, a deduction or a guide entry shown in it.