I can’t wrap my head around this, help!

Croftys

Back in April I locked in to a new 5 year rate of 4.24% on a mortgage of approx 45k to run over the next 20 years. All sounds pretty straight forward. 

In the last month of the previous term I paid 15k off, avoiding the ERC from Nationwide and the aim being to get 30k left to pay off within the 5 years and clear it with overpayments plus a lump in the last month. Voila. 

So using the mortgage calculators I worked out the monthly repayments at 230 ish a month using 30k as the mortgage amount, but when I looked at the actual mortgage payments they were at 268 ish. I worked out that the repayments are based on the 45k, so the overpayment is set aside. 

I can’t wrap my head around the difference in monthly payments, is it now lost in the void as a ‘cost’ of the 5 year mortgage?

Should I have overpaid the 15k spread over the previous mortgage deal , so the total would have been lower before the last month of the previous deal?

I’m working under the assumption that generally I’m saving interest at the end of the full term, but difference of the two repayments over 5 years can be as much at 3k, surely I haven’t just given that away? 

Please help!

BarelySentientAI

Your repayments have stayed the same but the speed at which your capital balance decreases has not.

More of each monthly payment is capital, less is interest.  You will need a smaller lump at the end because you will have less to pay off.

This is the less common of the two completely normal methods of calculation for when you make overpayments.  Actually, you have the opposite complaint from most people, who don't want their monthly repayments reduced but find that it has happened.

Monthly payment staying the same means the term has reduced - you are paying everything off faster.
Monthly payment decreasing means the term has stayed the same - you are paying it off at the same speed, but need a smaller cash flow to do it.

Probably happened because you effectively took a 45k mortgage when what you needed was a 30k mortgage.

GrumpyDil

Did they apply the 15k before the new mortgage started as it sounds slightly odd that the payments look to be based on the 45k amount rather than 30k?