Is there a limit on how much deposit I can take?
Yes — five weeks' rent, or six if the annual rent is £50,000 or more, and Tenarize rejects tenancy terms that exceed it rather than just warning you.
The Tenant Fees Act 2019 caps a tenancy deposit at five weeks' rent, rising to six weeks where the annual rent is £50,000 or more.
When you set the tenancy terms, Tenarize calculates the cap from the rent you've entered and refuses to save a deposit above it. That check runs on the server, so it applies however the terms are submitted — it isn't a client-side warning you can click past.
Worth knowing: Changing the rent later can bring an already-stored deposit above the cap. Tenarize re-checks the pair together, so a rent reduction that would break the cap is rejected too.
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Not legal advice
These answers describe how Tenarize works and summarise the law in England as the product implements it. They are not legal advice about your situation, and the law changes. For free independent help, Citizens Advice and Shelter both cover renting in England; for anything unusual or contested, take advice from a solicitor.
Tenarize does not currently support Scotland, Wales or Northern Ireland, whose tenancy regimes are different.