The cost of bankruptcy is £680 – this fee can be paid in instalments to the Insolvency Service via gov.uk until the £680 fee has been reached, so you can pay it at a rate that's affordable for you.
Once the fee has been paid in full, you will then be able to submit an application online.
Depending on your circumstances, a Debt Relief Order might offer a lower-cost alternative route into bankruptcy. It's intended for people with a very limited available income and few assets, and the application fee is £90. There is strict eligibility criteria which must be met to be able to apply for a DRO. Find out more here.