Skilled migrants using the 30% ruling have a net income that looks nothing like their gross figure, and lenders do not all treat that gap the same way. Because the ruling has a fixed lifespan, how a particular lender handles it is a question of fact to be checked rather than assumed.
It can, but there's no single rule — lenders differ on how they treat it. Some effectively gross up your income, treating the tax-free 30% allowance as if it were taxed income for borrowing-capacity purposes, which pushes your maximum mortgage up. Others stick to your net (post-ruling) income and ignore the tax break entirely, which is more conservative. A few land somewhere in between. Because the ruling has a fixed lifespan — currently a flat 30% for up to five years, though a change lands in 2027 that drops the rate to 27% for everyone still using the scheme, not just new applicants — some lenders also factor in how much runway you have left, since your net income drops once the benefit shrinks or ends and your mortgage payments don't. There's no way to generalize which bank will be most generous; it genuinely varies year to year and lender to lender. Comparing offers through a mortgage adviser, or asking a couple of banks directly what they do with 30%-ruling income, is the only reliable way to get your real number.