I live in the UK and use software from a US-based company. I currently pay a software licence fee of $150 every six months. This covers access to support and access to monthly software updates, new features, security and bug fixes.
They are now offering to let customers switch to a new pay monthly license, but there is a clause to the effect that if you should later deactivate your monthly license and take a break of less than two years, they will reactive your license upon request, but you agree to them charging you the backdated fees for all the months you missed.
If the deactivated license is not reactivated within two years, it will be considered cancelled and thus not be possible to reactive it; a brand new licence would be required.
Is it legal to backdate the monthly license fee for the missed payments, even though you have opted to forgo the normal active license benefits whilst your license is dormant?