Anything over your available spend will be added to your first payment at checkout. Pay the rest over 6 weeks. This will involve both making a credit payment, up to the value of your available balance, and debit payments, using the debit card you have registered with us, for the remaining amount.
For example, if your available spend is £200 and you use Zilch Boost to make a £300 purchase:
Your first payment (made at the time of purchase) would be £150.
This includes both your first Zilch re-payment of £50 (a quarter of your available spend) and the extra £100 you spent.
Your second, third and fourth instalment payments will each be £50.