When you apply for Medical insurance in Spain the insurance companies will ask you for your twenty digit Spanish bank account number or the IBAN.
Payments can be made annually, half-yearly, quarterly or even monthly with the majority of insurance companies in Spain. It is important to note that if the company agrees to you paying the annual amount in instalments you are legally obliged to pay all the instalments.
Note, that if you are applying for Spanish residency you will require an extra certificate from the insurer. This confirms the policy is without a co-payment as well as some other policy details. To get this certificate some companies, but not all, will insist you have paid the full annual amount and in these cases you will not have the options of a payment plan.
The vast majority of medical insurance companies in Spain run all their policies from 1st January to 31st December. If you sign up for a policy part way through the year you will only pay a pro-rata amount in the first year. Again, if they permit you to pay the pro-rata amount in instalments you are legally obliged to pay all the instalments.
If you choose a company that runs its policies from the month you apply and you pay annually, then you need to have available the full annual premium from the outset. With these companies there can be no pro-rata payment.
The companies require a Spanish bank account to collect the premium. However, if you are paying other than monthly it is possible with some of the medical insurance providers to pay the first instalment by debit or credit card from an overseas bank account or to make a bank transfer. Your bank details can be updated later.