tax_band before 2017-18 puts the higher band at £150,000, so 2016-17 higher-rate taxpayers get the Marriage Allowance #2356

What the law says

A person can receive the Marriage Allowance only if none of their income is charged at the higher or additional rate (ITA 2007 s. 55B). In 2016-17 the higher rate applied above a £32,000 basic rate limit.

What the model does

tax_band's first formula, which covers periods before 2017-04-06 and so the periods 2016 and 2017, places the bands at allowances + thresholds[0], allowances + thresholds[-2] and allowances + thresholds[-1]. In 2016 rates.uk.thresholds is [0, 32,000, 150,000, 10,000,000], so:

• the higher band starts at £150,000 above the allowances;
• the additional band starts at £10,000,000.

A higher-rate taxpayer is labelled BASIC. meets_marriage_allowance_income_conditions reads tax_band, so they pass.

Minimal reproduction

policyengine-uk main at c6d15c8: a married couple in England, one earning £60,000 and the other £5,000.

from policyengine_uk import Simulation
year = 2016
sit = {"people": {"a": {"age": {year: 40}, "employment_income": {year: 60_000}}, "b": {"age": {year: 40}, "employment_income": {year: 5_000}}},
       "benunits": {"u": {"members": ["a", "b"], "is_married": {year: True}}}, "households": {"h": {"members": ["a", "b"], "country": {year: "ENGLAND"}}}}
Simulation(situation=sit).calculate("marriage_allowance", year)  # [1060., 0.]; law: nil for a higher-rate recipient

Fix

Use thresholds[1] and thresholds[2] in the pre-2017 formula, as the 2017-04-06 formula does. #2348 stops the Personal Savings Allowance reading tax_band, so after it, Marriage Allowance is the only remaining reader.

Found in review of #2348.