How the numbers work
How Lenders Assess Part-Time Income
The calculation is straightforward. A lender takes your gross annual income from your payslips and P60, multiplies it by an income multiple (typically 4 to 4.5 times) and arrives at the maximum mortgage. The number of hours you work does not feature in that calculation.
Where it gets more complicated is what else gets included alongside the basic salary. Most lenders will use guaranteed basic pay without question. Additional elements such as overtime, shift allowances and secondary income are treated differently depending on the lender.
| Income type | How most lenders treat it | Documents needed |
| Basic part-time salary | Fully included at the contract rate | 3 months payslips, P60 |
| Guaranteed overtime or hours | Included if shown consistently on payslips for 3 to 6 months | Payslips showing the hours |
| Regular non-guaranteed overtime | Some lenders include 50%; others exclude entirely | 6 to 12 months payslips |
| Shift allowances | Included if contractual and consistent | Contract and payslips |
| Second part-time job | Included by most lenders with 3 to 6 months history | Payslips from both employers |
| Child benefit / tax credits | Some lenders include; others exclude | Award letters or bank statements |
| Zero hours contract income | Accepted by some specialist lenders with 12 months payslip history | 12 months payslips, P60 |
The income multiple matters as much as the income
Most lenders lend 4 to 4.5 times income. Some go to 5 or 5.5 times for applicants with higher incomes or certain professions. On a part-time income of £20,000 the difference between 4x (£80,000) and 5x (£100,000) is significant. A broker who knows which lenders apply higher multiples for your income level can make a real difference to what you can borrow.