# property.rental-yield
The two headline numbers for a let property:
- **Gross yield**: annual rent as a share of the property's value.
- **Net yield**: annual rent less the landlord's running costs, as a share of
the value.
Both are integer basis points (600 = 6.00%), rounded half-up (a half basis
point away from zero), once, from the exact ratio. The net income behind the
net yield is returned too, so a caller never recomputes it.
## Edge cases
- Costs above the rent give a negative net yield and a negative net income;
that is an answer, not an error.
- A zero rent gives a zero gross yield.
- All three amounts must be in one currency, and the value must be greater
than zero.
## What it does not do
Mortgage interest, tax, voids and capital growth are the caller's to fold into
the costs (or not). "Net yield" has no statutory definition; this is the plain
(rent − costs) / value that letting agents quote. Rent and value up to
£900 million keep the arithmetic exact in every language.
## Before you rely on this
**Not professional advice.** This capability calculates property figures from published rules. It is a software component for developers, not legal or financial advice. Rules change and every rate here has an effective date. Check that the dates cover your case. Verify results against the official sources listed above, and have a conveyancer or tax adviser review how you use it, before anyone relies on the output. Provided "as is" under its licence, without warranty.
**Unreviewed.** This capability's implementations agree in every language and pass its published test vectors, which were worked out from the official sources cited. But no qualified conveyancer or tax adviser has yet checked those vectors, or confirmed that the capability covers the cases it claims. Treat it as a draft. Do not use it for real people, money or decisions without your own expert review. Once a qualified reviewer signs off, this notice is replaced with their name, qualification and the date. Each new version needs fresh sign-off.
1.0.1 marks it unreviewed. The code and the tests are unchanged.