Many mortgage lenders in the Uk have moved to ‘affordability based lending’ from the traditional ‘income multiple’ Essentially, the lender will subtract your total monthly expenses away from your total monthly income - the amount that is left must be enough to cover the monthly payment according to their calculations.

For many, the maximum mortgage available from a particular lender may be difficult to establish – some lenders have tried to improve certainty by publishing ‘affordability calculators’ on their websites, but to get the right result you need to know what to put in the boxes in the first place.

1 – Credit Commitments

Always declare the exact amount you have outstanding on loans and credit cards (remember HP agreements and car loans), the monthly payment and how long is left to run on your agreement.

The monthly payment on a loan or minimum payment on your credit card (assuming a rate of around 5% of the balance per month) can have a major affect on the affordability calculation. If your loan has less than 6 months to run or you are able to settle in full some lenders will not include the payment in their calculations

2 – Income - if you are Employed

Being as precise as possible on your income is very important, overstating is never wise and not being accurate is just as bad. Always use the numbers off your payslips, bank statements and your and P60 as this is where the lender will look for evidence of your income.

If there are deductions from your salary other than tax & NI (season ticket loan or a pension) make sure you mention these at the point of application - some lenders may deduct these from your income and some don’t. Being accurate at the outset will reduce the chances of an lower mortgage offer than you expected which could cause problems if you are aiming for your maximum mortgage.

Bonuses, overtime, commissions and second jobs are used at different rates by different lenders. Most will only accept 50% (less for annual bonuses) and there will need to be a track record of usually a couple of years. Again speak to your broker or lender for advice.

3 – Income – if you are self employed

You may be surprised to hear that self certification and fast track mortgages have become slightly more difficult to find. All this means in reality is that you will have to do a little more work than finding a broker who was stupid enough to make up your income for you!

If you are self employed lenders will want to see at a minimum your last 2 years tax returns and SA302s (as your accountant if you don’t know what this is.) Typically they will average the last 2 years taxable income and use this figure as the start point on their affordability calculation.

If you are a director of a limited company (or partner in an LLP) the lender will, in most circumstances, use your salary and dividend (or net drawings) not your share of net profit. This distinction is very important (unless you own more than 51% of the shares in which case the rules are different).

Our advice is get your accounts before you apply and read through them. Alternatively, ask your accountant to write down your net profit, salary, dividends or drawings for the last 3 years on one page so you can see them.

If you are self employed, getting advice from a good broker will make all the difference – many of the lenders we speak too still cannot read a simple set of accounts and some of the better ones will be able to convince a lender to use retained profit or accountant’s tricks in their calculations/

4 – The Mortgage Term

How much you can borrow depends on how much you can pay back per month. Your monthly payment depends on how long you arrange your mortgage over. Lenders (almost) always base their calculations on a repayment basis to your retirement age. Before you apply find a mortgage payment calculator and find out how much your mortgage will be over various terms and find the one which is most suitable to you.

Remember – the longer the term, the more you can borrow. The shorter the term, the less it will cost you in interest. The latter is the most important.