If you are eligible for a visa or British Citizenship - apply before April to save the money!
The current ILR fee is £1,500 postal or £1,900 same-day service. From 18th March it will be £1,875 and £2,375 respectively (and the difference is being increased to £500) and that is per person, ie per each dependant!
If you are applying inside the UK and planning to use same-day service, your appointment has to be booked before 18th March, this is where you’d need to pay a Home Office fee and if applicable, a health surcharge.
If you are applying inside the UK and planning to use postal service for a visa application (but not Citizenship) the date of application will be the date of posting, if your application is sent by Royal Mail. Therefore, you will pay a fee applicable on the day of posting, even if the UK Visas and Immigration receives your case on or after 18th March. In case of applying for British Citizenship the date of application will be the date of delivery.